Core Techniques of Minimally Invasive Spine Surgery 9811998485, 9789811998485

Citation preview

Core Techniques of Minimally Invasive Spine Surgery Yong Ahn Jin-Kyu Park Chun-Kun Park Editors

123

Core Techniques of Minimally Invasive Spine Surgery

This is the official textbook to celebrate the 20th anniversary of the Korean Minimally Invasive Spine Surgery Society (KOMISS).

Yong Ahn  •  Jin-Kyu Park Chun-Kun Park Editors

Core Techniques of Minimally Invasive Spine Surgery

Editors Yong Ahn Department of Neurosurgery Gil Medical Center, Gachon University College of Medicine Incheon, Korea (Republic of)

Jin-Kyu Park Park Medical Center Pyeongtaek-si, Kyonggi-do Korea (Republic of)

Chun-Kun Park Department of Neurosurgery Seoul St. Mary’s Hospital, Catholic University of Korea Seoul, Korea (Republic of)

ISBN 978-981-19-9848-5    ISBN 978-981-19-9849-2 (eBook) https://doi.org/10.1007/978-981-19-9849-2 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Since the year 2000, there have been evolved some monumental technologies in the field of minimally invasive spine surgery (MISS), including percutaneous pedicle screw fixation, the use of tubular retractors, and endoscopic spine surgery. The common characteristic of these techniques is the percutaneous approach instead of conventional open access, which leads to extensive musculoskeletal trauma. Owing to the tissue preserving or percutaneous surgical process, patients could have a better quality of life with earlier recovery and less surgical morbidity. Therefore, MISS has now become an essential technique, not only an innovative procedure. I believe that today’s MISS will become tomorrow’s standard technique. Therefore, spine surgeons must learn and perform these innovative techniques in actual practice. This book aimed to provide a comprehensive textbook covering all core techniques of modern MISS. I truly appreciate all the contributing authors for their effort and energy in this voluminous work. Also, I want to express my special thanks to Dr. Shih-Min Lee for his dedication to the editing process. We couldn’t have managed without you. I hope this book will serve as a standard textbook for trainees and an essential reference for experienced spine surgeons. Finally, I am sending my love to Hwa-Young, Ji-Sun, and Seong-Woo. Yong Ahn

v

Preface

The treatment of spinal diseases has evolved significantly over the last few decades with the development of new instrumentation and surgical approaches as well as the adaptation of innovative technology. Minimally invasive spine surgery (MISS) has been at the center of these advancements. In the early days, minimally invasive surgery was performed by a minority of trained spinal surgeons due to its limited application and the high recurrence rate. Since then, there has been a significant progression in the field of MISS. One of the major breakthroughs in the field of MISS was its application. In the past, the MISS was only used to treat a limited number of lumbar pathologies. The application of MISS has progressed to include the treatment of complex spinal pathologies such as spinal tumors, spinal deformities, and spinal trauma. In addition, MISS is currently used to treat most spinal lesions successfully including cervical and thoracic spinal lesions as well as pathologies in the cranio-cervical junction which were previously treated with open surgery. KOMISS (Korean Minimally Invasive Spine Surgery) has made a major contribution to the development and breakthrough in the field of MISS. It is a great pleasure to have this textbook published in a year commemorating the 20th anniversary of the establishment of KOMISS. Congratulations and thanks to all the editors and authors who have contributed to the completion of the first comprehensive textbook published in South Korea that includes everything about minimally invasive surgery from its history to the most up-to-date surgical techniques. A special thanks to our editor-in-chief, Professor Ahn Yong, for all his work and contribution. We believe that this book will be of great help to many spinal surgeons, trainees, and students who wish to learn about MISS and will contribute to the development of MISS in the future. Pyeongtaek-si, Kyonggi-do, Republic of Korea

Jin-Kyu Park

vii

Preface

This textbook is the first edition published in English by KOMISS. In fact, KOMISS had already published a textbook of minimally invasive spine surgery (MISS) in 2012/6/15, only in Korean. Many spine surgeons in foreign countries were willing to have an English edition of this book, when they saw it first. Considering the reputation of KOMISS in the world community of MISS, KOMISS should had published an English textbook earlier. In any case, KOMISS ended up publishing an English one in time for the 20th Anniversary of KOMISS’s inauguration. It took about 2 years for writing and compilation. This textbook should be a fruit of efforts of the editorial committee and the chair of the committee, Professor Yong Ahn. Most of surgical techniques, devices, and approaches presented in the book are the ones most Korean MISS surgeons are practically using today. Please, the readers, be focused on the sectors of an endoscopic spine surgery (ESS) in the book, as Korean ESS had developed various kinds of novel techniques and published their clinical results in a world-renowned scientific journal. I hope readers will be pleased in the authors’ regards, which lead them to understand those techniques and their clinical applications better. KOMISS really wishes this book becomes globally useful and aids especially young spine surgeons who firstly intend to apply MISS in his/her practice. KOMISS should try to publish the next edition of MISS textbook in English betimes. Nowadays, development of medical science appears to be so fast that the book should not get left behind. Seoul, Republic of Korea

Chun-Kun Park

ix

Contents

Part I Introduction  istory of Minimally Invasive Spine Surgery ��������������������������������������   3 H Chun-Kun Park, Seong-Kyun Jeong, and Yong Ahn Basic Concepts and Nomenclature of Minimal Invasive Spine Surgery ������������������������������������������������������������������������������������������  13 Jin-Kyu Park Learning Curve and Complications of Minimally Invasive Spine Surgery ������������������������������������������������������������������������������������������  15 Yong Ahn Part II Endoscopic Spine Surgery  istory and Basic Concepts of Full-­Endoscopic Spine Surgery����������  23 H Sang Gu Lee  ransforaminal Endoscopic Lumbar Discectomy��������������������������������  29 T Yong Ahn I nterlaminar Endoscopic Lumbar Discectomy ������������������������������������  39 Gun Choi  ull Endoscopic Decompression in Thoracolumbar Stenosis��������������  49 F Chul Woo Lee and Hyeun Sung Kim Transforaminal Endoscopic Lumbar Lateral Recess Decompression������������������������������������������������������������������������������������������  63 Sang-Ha Shin Transforaminal Endoscopic Lumbar Foraminotomy/Foraminoplasty��������������������������������������������������������������  71 Jung-Hoon Kim, Jin-Sung Kim, Young-Jin Kim, and Kyung-Sik Ryu  nterior Percutaneous Endoscopic Cervical Discectomy��������������������  83 A Yong Ahn, Han Joong Keum, and Shih-Min Lee  ull Endoscopic Posterior Cervical Spinal Surgery ����������������������������  91 F Ji Yeon Kim and Dong Chan Lee xi

xii

Transforaminal Endoscopic Thoracic Discectomy and Decompression���������������������������������������������������������������������������������� 111 Junseok Bae  istory and Basic Concepts of Unilateral Biportal H Endoscopic Surgery (UBE) �������������������������������������������������������������������� 119 Dong-Geun Lee, Jae-Won Jang, and Choon-Keun Park Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis���������������������������������������������������������������������������������������������� 131 Sang-Kyu Son and Man Kyu Park Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine���������������������������������������������������������������������������������� 143 Nam Lee Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion���������������������������������������������������������������������� 157 Hyeun Sung Kim  iportal Endoscopic Lumbar Interbody Fusion���������������������������������� 167 B Dong Hwa Heo, Don Young Park, and Young Ho Hong Part III Minimally Invasive Spinal Procedure  verview of Minimally Invasive Spine Surgery with the Tubular O Retractor�������������������������������������������������������������������������������������������������� 179 Jong Un Lee and Dae-Hyun Kim  inimally Invasive Spinal Decompression for Lumbar Spine������������ 193 M Hanyu Seong, Sungryong Lim, and Il Choi  inimally Invasive Spinal Decompression for Cervical Spine������������ 211 M Chang-Il Ju and Se-Hoon Kim Minimally Invasive Transforaminal Lumbar Interbody Fusion�������������������������������������������������������������������������������������� 221 Dalsung Ryu and Jeong-Yoon Park  nterior Lumbar Interbody Fusion (ALIF)������������������������������������������ 237 A Kyeong-Sik Ryu  blique Lumbar Interbody Fusion (OLIF)������������������������������������������ 243 O Dongwuk Son and Suhun Lee  inimally Invasive Adult Spinal Deformity Correction���������������������� 267 M Junseok Bae  pinal Blocks and Radiofrequency Techniques������������������������������������ 275 S Seungchan Yoo and Jong Tae Kim  ercutaneous Epidural Neuroplasty������������������������������������������������������ 289 P Seon-Jin Yoon and Dong Ah Shin

Contents

Contents

xiii

Percutaneous Transforaminal Annuloplasty ���������������������������������������� 297 Shih-Min Lee  ELD, Trans Sacral Epiduroscopic Lumbar Decompression�������������� 307 S Kang Taek Lim  ertebroplasty and Kyphoplasty������������������������������������������������������������ 319 V Seong Son Part IV Motion Preservation Techniques  istory and Bascic Concepts of Motion Preservation Tehniques�������� 337 H Seung Myung Lee  rtificial Disc Replacement for Cervical Spine������������������������������������ 341 A Jung-Woo Hur, Doo Yong Choi, and Seungchan Yoo  otal Disc Replacement in Lumbar Degenerative Disc Diseases�������� 349 T Kang-Jun Yoon, Chul-Woo Lee, and Woon-Kyo Jung  osterior Dynamic Stabilization (Interspinous Process Device)���������� 369 P Je Il Ryu and In-Suk Bae  osterior Dynamic Stabilization (Screw and Dynamic Rod) �������������� 373 P Seungjun Ryu and Ho Yeol Zhang Part V New Technologies in Minimally Invasive Spine Surgery  avigation Guided Spine Surgery���������������������������������������������������������� 385 N Young San Ko and Chi Heon Kim  obotic Spine Surgery���������������������������������������������������������������������������� 399 R Chang Kyu Lee and Seong Yi  rtificial Intelligence and Minimally Invasive Spine Surgery������������ 411 A Heeseok Yang

Part I Introduction

History of Minimally Invasive Spine Surgery Chun-Kun Park, Seong-Kyun Jeong, and Yong Ahn

1 Introduction Small is beautiful. Less is better.

The description of minimally invasive spinal surgery (MISS) can be summarized in this sentence. Reducing the patient’s pain, accelerating recovery, and preventing degenerative changes and instability due to damage to normal tissues have been the concerns of many spine surgeons since the beginning of modern spine surgery. Thanks to the invention of various surgical methods and the development of surgical instruments, current spine surgery makes it possible to treat a wider area of the spine with fewer incisions and minor structural damage. The scope of the MISS target range has been widened from simple percutaneous procedures not covered by conventional surgical methods to diseases that have been treated with traditional C.-K. Park (*) Department of Neurosurgery, Seoul St. Mary’s Hospital, Catholic University of Korea, Seoul, Republic of Korea e-mail: [email protected] S.-K. Jeong Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Republic of Korea Y. Ahn Department of Neurosurgery, Gil Medical Center, Gachon University College of Medicine, Incheon, Republic of Korea

surgical methods, such as tumors and deformities. Just as laparoscopic cholecystectomy surgery has been established as the standard treatment for symptomatic cholelithiasis in general surgery, and robotic surgery for prostate cancer is actively performed in urology, the era has come when minimally invasive surgery should be considered as the first option in spinal surgery. Although at the stage of development of MISS, some treatments were regarded as treatments lacking evidence or were discontinued due to fatal side effects, spine surgeons did not get frustrated and overcame numerous trials and errors. MISS has reached the position of scientific, well-established, and genuinely patient-­ friendly treatment that should not be biased against commercial or unscrupulous care [1]. In this chapter, we are going to try to understand the current address of MISS by introducing various treatments that have appeared from the beginning to the present and examining their significance.

2 The Beginning of MISS In 1963, Smith became the world’s first physician to attempt percutaneous disc therapy [2]. He reported that intradiscal pressure could be lowered by injecting the Chymopapain, an enzyme extracted from the fruit of Carica papaya, into human intervertebral discs. This method, called

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_1

3

C.-K. Park et al.

4

chemonucleolysis, was performed on thousands of patients until 1984 but was no longer performed due to fatal hypersensitivity reactions and transverse myelitis [3]. However, this treatment provided a starting point for the future development of intervertebral disc therapy. In 1977, Yasargil and Caspar performed the first microscopic surgeries for a herniated lumbar disc [4]. Neurosurgeons already accustomed to microscopy in brain surgery quickly accepted that microscopic surgery could be helpful in disc removal. To brighten intervertebral disc lesions located deep under the fascia, a large incision and wide dissection were required in conventional surgery with naked eyes. However, using a microscope for intervertebral disc disease has made it possible to perform surgery with fewer incisions and a more magnified and brighter field of view. Although microscopic

discectomy is now recognized as the standard treatment for disc herniation, it was a groundbreaking minimally invasive surgical (MIS) method at that time. In 1973, Kambin became the first surgeon to operate percutaneously on an intervertebral disc [5]. He used Craig cannula, initially used for bone biopsy, for decompression of an intervertebral disc during his open lumbar discectomy. He has been continuously researching methods for percutaneous disc surgery. He reported in 1988 on a “safe triangular working zone” [6], which is called Kambin’s triangle and is a monumental discovery in the development of endoscopic spine surgery (ESS) using the transforaminal approach (Fig. 1). Each method is currently leading to intradiscal therapy, MIS decompression and fusion, and ESS, which are representative fields of MISS.

Fig. 1  The Kambin’s triangle and its boundary

Exiting nerve Root

Kambin's triangIe

Superior vertebraI endpIate

Superior ArticuIar process

History of Minimally Invasive Spine Surgery

5

3 Endoscopic Spine Surgery (ESS) ESS is a method optimized for the MISS principle and occupies a large part of MISS. In the past, the treatment was attempted only for contained herniated discs of the lumbar spine. Nevertheless, now it is possible to treat migrated discs and lesions of the thoracic and cervical spine, and even decompression and fusion for stenosis can be achieved through ESS. In the 1970s, Kambin and Hijikata tried a method for percutaneous disc surgery, respectively [7, 8]. However, they were blind procedures without direct visualization. In the field of orthopedic surgery, arthroscopic surgery has been performed since 1950 by Watanabe et  al. [9]. Since the 1980s, Kambin has attempted percutaneous disc surgery by using arthroscopy. So, at that time, Kambin reported his endoscopic surgery as “arthroscopic microdiscectomy” [8]. In order to operate an intervertebral disc with an endoscope, specialized methods are needed to specify the target lesion during the surgery. In 1988, Kambin reported patterns of intraoperative discography [10]; in 1989, Schreiber et  al. reported a disc staining method using indigo carmine [11]. These methods are used in ESS until now. In 1991, Leu with Karl Storz introduced an endoscope that allows direct visual inspection of the inside of the intervertebral disc [12]. They developed a “foraminoscope” for use in the bilateral biportal approach. Since it is reusable, the “foraminoscope” has been used on the market for a long time [13]. In 1993, Meyer first termed “PELD (percutaneous endoscopic lumbar discectomy)” for his ESS using the foraminoscope [14]. In 1996, Mathew introduced the first fiber-optic endoscope in collaboration with Danek [15]. However, it was not reusable and relatively high-­ cost, so it soon disappeared from the market [13]. Around 2000, two innovative endoscopic surgical methods and instruments appeared in the transforaminal endoscopic lumbar discectomy (TELD) (Fig. 2). In 1999, Anthony Yeung introduced an endoscopic instrument in collaboration with Richard Wolf [16]. This multichannel endo-

Fig. 2  Transforaminal endoscopic spine surgery (TELD)

scope capable of working channel, irrigation channel, and video CCD pickup simultaneously was called YESS (Yeung Endoscopic Spine System). In addition, Yeung introduced the “inside-out” technique to place the cannula inside the intervertebral disc at the start of endoscopic surgery. YESS is designed to be suitable for the “inside-out” technique. From 1999 to 2002, Thomas Hoogland with Joimax developed THESYS (Thomas Hoogland Endoscopic Spine System) [17]. Hoogland introduced a specialized reamer to expand the intervertebral foramen before disc removal. Hoogland’s method was known as “outside-in” in contrast to the previous method. Together with “inside-out,” these two methods later became the most famous basic principles of TELD. In 2007, Lee et al. reported a “half-and-half” technique combining the advantages of both methods [18]. This method was predominantly used by spine surgeons from Wooridul Spine Hospital in Korea. Currently, TELD is gaining much agreement with the view that customized treatment should be selected according to the location of the patient’s lesion rather than whether it is “inside-out” or “outside-in.” Many Korean spine surgeons have contributed to broadening the indications for endoscopic discectomy. In 2004, Ahn et al. reported the usefulness of TELD for recurrent lumbar disc herniation [19], and in 2005 anterior endoscopic cervical discectomy [20]. In 2008, Choi et al. reported a surgical method for severely migrated disc herniation using the foraminoplastic technique [21]. Transforaminal endoscopic thoracic discectomy was reported in 2010 by Choi et al.

C.-K. Park et al.

6

The endoscopic disc surgery performed in the Kambin triangle had several obstacles, including an approach for patients with high iliac crest and a decompression method for central or lateral recess stenosis. In 2005, Ruetten reported an idea that could solve this problem through the interlaminar approach and named it full-endoscopy [22]. This name has a meaning to distinguish it from microendoscopic or epiduroscopic procedures. And in 2007, Ruetten also reported a posterior cervical foraminotomy (PCF) using full-endoscopy [23]. Another approach for stenosis is unilateral biportal endoscopic surgery (UBE) (Fig.  3). In 2015, Soliman reported a method called irrigation endoscopic decompressive laminotomy for spinal stenosis decompression and tried the currently used UBE method for the first time [24]. This method was later known as BESS (biportal endoscopic spine surgery) and is now replaced by the term UBE to distinguish it from bilateral biportal endoscopic surgery used in the earlier period. As this method applied many microscopic surgical techniques, it is accepted as a technique that surgeons familiar with microscopic techniques can accept. Since Eum et al. reported on JNS spine in 2016 [25], many spine surgeons in Korea have been conducting UBE nationally. Thanks to their efforts, the indications have rapidly expanded to diseases that had to be resolved with conventional open surgery in the last few years [26]. As for the endoscopic fusion technique, the transforaminal method using Kambin triangle, the method using the transforaminal interbody

Fig. 3  Unilateral biportal endoscopic spine surgery (UBE)

fusion (TLIF) corridor introduced by Harms in open surgery (uniportal or biportal), and the indirect decompression only (+percutaneous screws) method using the oblique lumbar interbody fusion (OLIF) trajectory are being studied [27]. In 2017, lumbar endoscopic decompression was registered in the CPT 2017, the American Medical Association’s official coding resource and many university hospitals including the Unversity of Miami hospital and hospitals of Yale School of Medicine are also introducing ESS in their training course.

4 MIS Decompression and Fusion In 1977, Yasargil’s microscopic spine surgery was introduced and established as the standard treatment for many spine diseases. Afterward, a method to improve and produce the same or better treatment effect with a smaller incision was studied. In 1997, Foley et al. reported a surgical technique called microendoscopic discectomy (MED) using an endoscopic approach and microscopic procedures in the field of view [28] (Fig.  4). In this method, a tubular retractor equipped with an endoscope was fixed using a flexible arm, and then a microscopic surgical instrument was inserted into the tubular retractor for surgery. It was a good idea to perform surgery with a microscope instrument while viewing the endoscopic screen on a monitor, but it was challenging to match the field of view and work until mastery. In 1999, the METRx system was introduced, which improved the MED system. Instead of mounting the endoscope on the tubular retractor, this system is an improved product that allows the user to see the surgical field through a microscope, providing a more user-friendly environment [28]. In 1997, Spetsger et al. reported a method for unilateral laminotomy for bilateral decompression (ULBD) of lumbar spinal stenosis [29]. In this method, after dissection of the muscle on a single side, laminotomy is performed on the ipsilateral side. Then the decompression of the con-

History of Minimally Invasive Spine Surgery

7

Fig. 4 Microendoscopic discectomy (MED)

Rongeur Root retractor

Endoscope

TabIe-fixed arm Retractor tube

tralateral side is performed through sublaminar undercutting. In 2002, Fessler et al. performed ULBD using a tubular retractor to achieve decompression with minor damage to the skin and paraspinal muscles [30]. Magerl was the first surgeon who performed percutaneous screw fixation and fusion in 1977 [31]. In 1982, he reported his surgical technique of percutaneous screw insertion when C-arm imaging showed the pedicle’s long axis. The inserted screws were connected with temporary external spinal skeletal fixation until proper fusion had occurred [31]. From the current point of view, Magerl’s method seems to be a cumbersome surgical method with concerns about patient discomfort and infection due to external fixation. However, at that time, compared to open surgery using screws and plates, which fixed five vertebrae, including two levels above and below the index level, it was a surgical method that fur-

ther preserved the mobile segment by fixing only the three vertebrae. In 1999, Wiesner et al. reported a percutaneous pedicle screw method modified from Margerl’s [32]. This method is still widely used today and is a method of inserting a K-wire up to the junction of the pedicle and vertebral body using true AP and lateral images. The challenge of percutaneous screw fixation was how to connect and fix the screws. To solve this problem, Mathews et  al. connected screws with a plate in the endoscopic field of view in 1995 [33]. The person who solved this problem was Foley et al. in 2001, who developed and used a rod-fixing device that applied the sextant principle [34] (Fig.  5). Rods were connected without direct visualization under the aid of a C-arm. Since then, there have been more devices that connect the rods in various ways. They also

C.-K. Park et al.

8

ALIF

OLIF

DLIF

Fig. 5 Percutaneous screw fixation using Sextant™ system

improved the Harms technique and reported the first minimally invasive TLIF using a tubular retractor [34]. The first physician to insert an interbody cage percutaneously was Zucherman in 1995 [35]. He performed anterior lumbar interbody fusion (ALIF) through a transperitoneal approach using laparoscopy. However, laparoscopy was very difficult to master, so spine surgeons preferred the minimally invasive ALIF method introduced by Mayer in 1997 [36]. He used a retroperitoneal approach using a lateral decubitus position for L2–3, L3–4, and L4–5, and a transperitoneal approach with a supine position for L5–S1. Among them, the retroperitoneal approach was later called OLIF (Fig. 6). In 2006, Ozgur et  al. reported a surgical method to access the disc space across the psoas muscle and named it extreme lateral interbody fusion (XLIF) [37]. In 2009, Knight et al. reported a direct lateral interbody fusion (DLIF) surgery similar to XLIF but more streamlined [38]. The two methods differ only in the surgical instrument company, but the procedures are almost identical. In 2009, Santoni et al. reported a midline lumbar interbody fusion (MIDLIF) surgical method using only cortical bone by modifying the existing pedicle screw trajectory [39]. This method uses fewer skin incisions than conventional posterior lumbar interbody fusion (PLIF) surgery

TLIF PLIF Fig. 6  Interbody fusion methods according to the direction of the approaches

and is known to have advantages in surgery for osteoporotic patients. In 2021, Bae et  al. reported a transumbilical retroperitoneal lumbar interbody fusion method in which the incision is smaller than the minimally invasive ALIF [40]. As with the lumbar spine, the minimally invasive surgical (MIS) approach to the thoracic spine can be endoscopically or posteriorly using a tubular retractor. In 1997, Jho performed an endoscopic thoracic discectomy through a transpedicular approach [41]. However, an anterior approach is often required to resolve the lesion due to the nature of the thoracic spinal cord, which is vulnerable to compression and traction. The MIS anterior approach to the thoracic spine was first started after the experience of video-assisted thoracic surgery (VATS) in general thoracic surgery was accumulated. The first to try this was in 1993 by Mack et  al. [42]. They performed discectomy, fusion, biopsy, and abscess drainage using VATS in 10 patients from 1991 to 1993. In addition to using VATS, other MIS techniques to treat various thoracic lesions such as hard disc and OPLL by minimizing the scope of thoracotomy have been developed and implemented. The prognosis of patients is also satisfactory [43].

History of Minimally Invasive Spine Surgery

Anterior cervical discectomy and fusion (ACDF) occupy a firm position in cervical spine disease. These surgical methods have the advantage that, except for cosmetic parts, it rarely causes muscle damage, and there is almost no bleeding during surgery. Moreover, the anterior structures are full of structures that should not be injured in blind operation. The disadvantage is that fusion decreases motion. Alternative MIS techniques, except for endoscopic therapy, are anterior cervical foraminotomy (ACF) and PCF. Jho first reported the currently used ACF in 1996 [44], and he reported again in 2002 when he revised his technique [45]. In 2007, Choi et  al. reported modified transcorporeal ACF [46]. Regarding MIS PCF, Roh et  al. of the Fessler Group studied MED PCF using a tubular retractor in 2000 [47], and the clinical results of the same group were reported in 2002 [30]. In the recent decade, with the help of intraoperative O-arm and navigation equipment, it has been possible to access the lesion in a more accurate direction. Furthermore, spinal surgery using robot techniques or augmented reality is gradually starting.

5 Intradiscal Therapy Intradiscal therapy is the first treatment category in the history of MIS. Currently, ESS is mainly responsible for MIS treatment related to a herniated disc, but intradiscal therapy has provided several important ideas for application to endoscopic treatment during development. Although no longer being tried, chemonucleolysis started in 1963 confirmed the therapeutic potential of intradiscal decompression. In 1984, Choy et  al. reported percutaneous laser disc decompression (PLDD) using Nd:YAG laser [48], and in 1992 Davis reported his PLDD using KTP laser [49]. They had limitations that treating

9

disc herniation should be indirect and aims only at the center of the intervertebral discs rather than the prolapsed disc particles. However, it is meaningful that they tried to treat disc disease using laser, and their methods were relatively simple. Automated percutaneous nucleotomy was reported by Onik et al. in 1985, a device capable of suctioning many nucleus fragments with negative pressure after inserting a shaver inside the disc [50]. This method is also significant in that it attempted intradiscal decompression to treat disc disease without life-threatening hypersensitivity, which is the adverse effect of chemonucleolysis. Afterward, as ESS became the primary MIS treatment for herniated discs, intradiscal therapy was studied for chronic discogenic back pain. In 2000, Saal et al. reported intradiscal electrothermal treatment (IDET) and used a navigable catheter with a temperature-controlled thermal resistive coil inserted into the intervertebral disc [51]. The inserted heat wire coagulated intradiscal collagen to increase the intervertebral disc’s elasticity and reduce pain by destroying the nerve. Annuloplasty can now be performed endoscopically. In 2010, Lee et  al. pointed out that granulation tissue observed at the site of annular tear is the cause of discogenic back pain, and reported the result of endoscopic laser annuloplasty using Ho: YAG laser reduced discogenic back pain in 27 out of 30 patients [52]. In addition, several percutaneous intradiscal devices were introduced between the 1990s and 2000s, but the treatments except annulo/nucleoplasty disappeared due to concerns about their therapeutic efficacy and cost-effectiveness [1]. There are various causes of chronic back pain, including annular tears, facet joints, SI joints, and myofascial origin. The key to intradiscal therapy is to properly select the indications, treat the lesion accurately, and avoid reckless treatment based only on symptoms.

10

6 Other Percutaneous Treatment Galibert initially reported percutaneous vertebroplasty (PVP) in 1987 as a treatment for spinal hemangioma [53]. Then, in 1997, Jensen tried PVP using polymethyl methacrylate (PMMA) for osteoporotic compression fracture [54]. Later, it was also used to treat pain caused by metastatic spinal tumors. Kyphoplasty has only been used actively since the FDA approved the inflatable bone tamped in 1998. Reiley summarized this in 2001 [55]. He reported that kyphoplasty reduces acute fractures and allows the controlled placement of PMMA, improving deformity and pain. These methods are used as a treatment for fractures without neurological deterioration.

7 Summary MISS is not opposed to conventional spine surgery but an advanced surgical technique that pursues the best results for the patient. It is a treatment that minimizes the patient’s damage through technological advances and resolves unnecessary hesitation in the patient’s treatment. As MISS experience has been accumulated, it is now possible to replace many areas of open spine surgery with MISS. MISS has become an essential skill that spine surgeons should have. MISS will lead the future of spine surgery.

References 1. Park C-K.  Minimally invasive spine surgery in Korea—a neurosurgeon’s view. J Minim Invasive Spine Surg Tech. 2016;1(1):3–4. 2. Smith L. Enzyme dissolution of the nucleus pulposus in humans. JAMA. 1964;187:137–40. 3. Watts C, Dickhaus E.  Chemonucleolysis: a note of caution. Surg Neurol. 1986;26(3):236–40. 4. Koebbe CJ, Maroon JC, Abla A, El-Kadi H, Bost J.  Lumbar microdiscectomy: a historical perspective and current technical considerations. Neurosurg Focus. 2002;13(2):E3. 5. Khandge AV, Sharma SB, Kim JS.  The evolution of transforaminal endoscopic spine surgery. World Neurosurg. 2021;145:643–56.

C.-K. Park et al. 6. Kambin P, Zhou L. History and current status of percutaneous arthroscopic disc surgery. Spine. 1996;21(24 Suppl):57s–61s. 7. Hijikata S. Percutaneous nucleotomy. A new concept technique and 12 years’ experience. Clin Orthop Relat Res. 1989;238:9–23. 8. Kambin P.  Arthroscopic microdiscectomy. Arthroscopy. 1992;8(3):287–95. 9. Ikeuchi H. The early days of arthroscopic surgery in Japan. Arthroscopy. 1988;4(3):222–5. 10. Kambin P, Nixon JE, Chait A, Schaffer JL. Annular protrusion: pathophysiology and roentgenographic appearance. Spine. 1988;13(6):671–5. 11. Schreiber A, Suezawa Y, Leu H.  Does percutaneous nucleotomy with discoscopy replace conventional discectomy? Eight years of experience and results in treatment of herniated lumbar disc. Clin Orthop Relat Res. 1989;238:35–42. 12. Leu H, Hauser R.  Die perkutan posterolaterale Foraminoskopie: Prinzip, Technik und Erfahrungen seit 1991. Arthroskopie. 1996;6:926–31. 13. Tieber F, Lewandrowski K-U. Technology advancements in spinal endoscopy for staged management of painful spine conditions. J Spine Surgery. 2019;6:S19–28. 14. Mayer HM, Brock M. Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg. 1993;78(2):216–25. 15. Mathews HH.  Transforaminal endoscopic microdiscectomy. Neurosurg Clin N Am. 1996;7(1):59–63. 16. Yeung AT.  Minimally invasive disc surgery with the Yeung endoscopic spine system (YESS). Surg Technol Int. 1999;8:267–77. 17. Schubert M, Hoogland T. Endoscopic transforaminal nucleotomy with foraminoplasty for lumbar disk herniation. Oper Orthop Traumatol. 2005;17(6):641–61. 18. Lee S, Kim SK, Lee SH, Kim WJ, Choi WC, Choi G, et  al. Percutaneous endoscopic lumbar discectomy for migrated disc herniation: classification of disc migration and surgical approaches. Eur Spine J. 2007;16(3):431–7. 19. Ahn Y, Lee SH, Park WM, Lee HY, Shin SW, Kang HY.  Percutaneous endoscopic lumbar discectomy for recurrent disc herniation: surgical technique, outcome, and prognostic factors of 43 consecutive cases. Spine. 2004;29(16):E326–32. 20. Ahn Y, Lee SH, Shin SW.  Percutaneous endoscopic cervical discectomy: clinical outcome and radiographic changes. Photomed Laser Surg. 2005;23(4):362–8. 21. Choi G, Lee SH, Lokhande P, Kong BJ, Shim CS, Jung B, et al. Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique using rigid working channel endoscope. Spine. 2008;33(15):E508–15. 22. Ruetten S, Komp M, Godolias G.  A New full-­ endoscopic technique for the interlaminar operation of lumbar disc herniations using 6-mm endoscopes: prospective 2-year results of 331 patients. Minim Invasive Neurosurg. 2006;49(2):80–7.

History of Minimally Invasive Spine Surgery 23. Ruetten S, Komp M, Merk H, Godolias G.  A new full-endoscopic technique for cervical posterior foraminotomy in the treatment of lateral disc herniations using 6.9-mm endoscopes: prospective 2-year results of 87 patients. Minim Invasive Neurosurg. 2007;50(4):219–26. 24. Soliman HM.  Irrigation endoscopic decompressive laminotomy. A new endoscopic approach for spinal stenosis decompression. Spine J. 2015;15(10):2282–9. 25. Hwa Eum J, Hwa Heo D, Son SK, Park CK.  Percutaneous biportal endoscopic decompression for lumbar spinal stenosis: a technical note and preliminary clinical results. J Neurosurg Spine. 2016;24(4):602–7. 26. Heo DH, Park CW, Son SK, Eum JH. Unilateral biportal endoscopic spine surgery. Singapore: Springer; 2022. 27. Kim HS, Wu PH, Jang IT.  Current and future of endoscopic spine surgery: what are the common procedures we have now and what lies ahead? World Neurosurg. 2020;140:642–53. 28. Khoo LT, Fessler RG.  Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery. 2002;51(5 Suppl):S146–54. 29. Spetzger U, Bertalanffy H, Reinges MH, Gilsbach JM.  Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part II: clinical experiences. Acta Neurochir. 1997;139(5):397–403. 30. Perez-Cruet MJ, Foley KT, Isaacs RE, Rice-Wyllie L, Wellington R, Smith MM, et al. Microendoscopic lumbar discectomy: technical note. Neurosurgery. 2002;51(5 Suppl):S129–36. 31. Magerl FP.  Stabilization of the lower thoracic and lumbar spine with external skeletal fixation. Clin Orthop Relat Res. 1984;189:125–41. 32. Wiesner L, Kothe R, Rüther W.  Anatomic evaluation of two different techniques for the percutaneous insertion of pedicle screws in the lumbar spine. Spine. 1999;24(15):1599–603. 33. Mathews H.  Endoscopy assisted percutaneous anterior interbody fusion with subcutaneous suprafascial internal fixation: evolution of technique and surgical considerations. Orthopaedics. 1995;3:496–500. 34. Schwender JD, Holly LT, Rouben DP, Foley KT. Minimally invasive transforaminal lumbar interbody fusion (TLIF): technical feasibility and initial results. J Spinal Disord Tech. 2005;18(Suppl):S1–6. 35. Zucherman JF, Zdeblick TA, Bailey SA, Mahvi D, Hsu KY, Kohrs D.  Instrumented laparoscopic spinal fusion. Preliminary results. Spine. 1995;20(18):2029– 34; discussion 34–5. 36. Mayer HM.  A new microsurgical technique for minimally invasive anterior lumbar interbody fusion. Spine. 1997;22(6):691–9; discussion 700. 37. Ozgur BM, Aryan HE, Pimenta L, Taylor WR.  Extreme Lateral Interbody Fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion. Spine J. 2006;6(4):435–43. 38. Knight RQ, Schwaegler P, Hanscom D, Roh J. Direct lateral lumbar interbody fusion for degenerative con-

11 ditions: early complication profile. J Spinal Disord Tech. 2009;22(1):34–7. 39. Santoni BG, Hynes RA, McGilvray KC, Rodriguez-­ Canessa G, Lyons AS, Henson MA, et  al. Cortical bone trajectory for lumbar pedicle screws. Spine J. 2009;9(5):366–73. 40. Bae J, Kim SJ, Lee SH, Bae Y, Jeon SH. Transumbilical retroperitoneal lumbar interbody fusion: a technical note and preliminary case series. Neurospine. 2021;18(2):399–405. 41. Jho HD.  Endoscopic microscopic transpedicular thoracic discectomy. Technical note. J Neurosurg. 1997;87(1):125–9. 42. Mack MJ, Regan JJ, Bobechko WP, Acuff TE.  Application of thoracoscopy for diseases of the spine. Ann Thorac Surg. 1993;56(3):736–8. 43. Lee S-H, Bae J, Jeon S-H.  Minimally invasive thoracic spine surgery. Singapore: Springer; 2021. 44. Jho HD.  Microsurgical anterior cervical foraminotomy for radiculopathy: a new approach to cervical disc herniation. J Neurosurg. 1996;84(2):155–60. 45. Jho HD, Kim MH, Kim WK. Anterior cervical microforaminotomy for spondylotic cervical myelopathy: part 2. Neurosurgery. 2002;51(5 Suppl):S54–9. 46. Choi G, Lee SH, Bhanot A, Chae YS, Jung B, Lee S.  Modified transcorporeal anterior cervical microforaminotomy for cervical radiculopathy: a technical note and early results. Eur Spine J. 2007;16(9):1387–93. 47. Roh SW, Kim DH, Cardoso AC, Fessler RG. Endoscopic foraminotomy using MED system in cadaveric specimens. Spine. 2000;25(2):260–4. 48. Choy DS, Ascher PW, Ranu HS, Saddekni S, Alkaitis D, Liebler W, et al. Percutaneous laser disc decompression. A new therapeutic modality. Spine. 1992;17(8):949–56. 49. Davis JK.  Early experience with laser disc decompression. A percutaneous method. J Fla Med Assoc. 1992;79(1):37–9. 50. Onik G, Maroon J, Day A, Helms C. Automated percutaneous discectomy: preliminary experience. Acta Neurochir Suppl. 1988;43:58–62. 51. Saal JA, Saal JS.  Intradiscal electrothermal therapy for the treatment of chronic discogenic low back pain. Clin Sports Med. 2002;21(1):167–87. 52. Lee SH, Kang HS.  Percutaneous endoscopic laser annuloplasty for discogenic low back pain. World Neurosurg. 2010;73(3):198–206; discussion e33. 53. Galibert P, Deramond H, Rosat P, Le Gars D. [Preliminary note on the treatment of vertebral angioma by percutaneous acrylic vertebroplasty]. Neuro-­ Chirurgie. 1987;33 (2):166–8. 54. Jensen ME, Dion JE. Vertebroplasty relieves osteoporosis pain. Diagn Imaging. 1997;19(9):68, 71–2. 55. Garfin SR, Yuan HA, Reiley MA. New technologies in spine: kyphoplasty and vertebroplasty for the treatment of painful osteoporotic compression fractures. Spine. 2001;26(14):1511–5.

Basic Concepts and Nomenclature of Minimal Invasive Spine Surgery Jin-Kyu Park

1 Introduction

2 Main Text

Advances and evolution in technology and surgical techniques have led to the establishment of minimally invasive approaches in various surgical fields including spine surgery. Minimally invasive surgical techniques have revolutionized the field of spine surgery. In parallel with technological advancements including imaging, endoscopy, and navigation systems, minimally invasive techniques have also progressed significantly. Currently, MISS techniques are used in the treatment of various spinal pathologies. The application of MISS was initially limited to treating lumbar disc diseases such as disc herniation and spinal stenosis. The use of MISS has been reported in conditions such as spine deformities and metastatic spine disease which were traditionally treated with open surgeries. Although the exact definition of minimally invasive spine surgery (MISS) is yet to be agreed upon, the core principles remain consistent. MISS aims to treat spinal conditions effectively while minimizing some of the drawbacks associated with open surgeries like collateral soft tissue damage, blood loss, increased hospital stay, and postoperative morbidity.

The dictionary definition of the term “minimally invasive” is “involving as little incision into the body as possible.” As this definition implies, one of the underlying principles of minimally invasive surgery is performing surgery through a small surgical window. This reduces any muscle and soft tissue damage associated with surgical exposure. Another key principle of MISS includes the minimization of any collateral injury to the musculoskeletal system as well as the preservation of normal anatomical structures [1]. This can lead to a reduced hospital stay and postoperative pain which in turn is associated with overall patient outcomes. There has been an evolution in technology and surgical techniques over the last few decades that allowed spine surgeries to be performed via a minimal surgical window. Several percutaneous techniques have been developed, starting with the discovery of chymopapain and its chemonucleolytic property. Smith successfully used chymopapain to treat lumbar disc herniation. Other percutaneous approaches in MISS include percutaneous nucleotomy, laser discectomy, and the development of the nucleotome [2]. One of the major technological advancements in MISS is the development of the tubular retractor system in microdiscectomies. This technology allowed the preservation of midline muscle and ligament structures. The application of the tubular retrac-

J.-K. Park (*) PMC Park Hospital, Pyeongtaek-si, Gyeonggi-do, Republic of Korea

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_2

13

J.-K. Park

14

tor system has been reported in various surgeries from lumbar discectomy and canal decompression [3]. Along with the evolution of surgical equipment, the percutaneous screw placement technique was developed. This technique is applied in a variety of surgeries, most notably in interbody fusion, spine deformity correction surgeries, and spine trauma treatment [4]. Another milestone in the field of MISS was the application of endoscopes in spine surgeries. The first adaptation of endoscopic spinal surgery was percutaneous endoscopic lumbar discectomy where the procedure was not under direct visualization. Later Yeung used the Yeung endoscopic spine system which could visualize the lesion directly [5]. The field of endoscopic spine surgery has grown significantly since then. Endoscopic spine surgery can now be used to treat the whole spine. The application of endoscopic techniques in spine surgery includes endoscopic lumbar discectomy through transforaminal and interlaminar approaches as well as endoscopic decompression in the treatment of spinal stenosis, endoscopic interbody fusion, and endoscopic treatment of intradural lesions which has also shown great promise [6].

3 Summary The main concept underlying minimally invasive spine surgery is to minimize muscle and soft tissue damage while achieving equal or improved outcome compared to traditional open surgeries.

This allows the preservation of normal spinal function thus reducing postoperative pain and recovery time as well as improving overall patient outcomes. In the past, the term “minimally invasive spine surgery” was mainly associated with discectomies performed through endoscopic and microendoscopic approaches. As the application of MISS evolved with the development of technology and surgical approaches, the use of this term has expanded. The term MISS can be used to describe a wide range of spine surgeries including endoscopic spine surgery, open microdiscectomy as well as spine deformities and metastatic spine disease. The application of MISS techniques will continue to grow with further evolution in imaging, navigation, and robotics.

References 1. Yoon JW, Wang MY. The evolution of minimally invasive spine surgery: JNSPG 75th Anniversary Invited Review Article. J Neurosurg Spine. 2019;30:149–58. 2. Smith L, Garvin PJ, Gesler RM, Jennings RB. Enzyme dissolution of the nucleus pulposus. Nature. 1963;198:1311–2. 3. Jaikumar S, Kim DH, Kam AC. History of minimally invasive surgery. Neurosurgery. 2002;51(S1–S4):5. 4. Thongtrangan I, Le H, Park J, Kim DH.  Minimally invasive spinal surgery: a historical perspective. Neurosurg Focus. 2004;16:1–10. 5. Yeung AT.  Minimally invasive disc surgery with the Yeung endoscopic spine system (YESS). Surg Technol Int. 1999;8:267–77. 6. Kim CW, Phillips F. The history of endoscopic posterior lumbar surgery. Int J Spine Surg. 2021;15:S6–S10.

Learning Curve and Complications of Minimally Invasive Spine Surgery Yong Ahn

1 Introduction Recently, various minimally invasive spine surgery (MISS) techniques have gained attention in the spinal surgery community because of the need to maintain the quality of life of the patient and the search for rapid recovery after surgery. Using a tubular retractor system and percutaneous instrumentation during surgery could reduce unnecessary surgical exposure and tissue damage in traditional open surgery. This tissue preservation approach may ensure sufficient surgical results, fewer adverse events, and an earlier return to work [1–8]. However, critical entry barriers and learning curves must be overcome. Standard spine surgeons are unfamiliar with MISS and require extensive training to obtain optimal clinical results. The training process should proceed until the cut-off point or asymptote of the learning curve is reached. One of the most common causes of steep learning is the unique complications of MISS. Dural tears, incomplete decompression or recurrence, instrument malposition, hematoma,

and infection should be prevented or managed adequately. This chapter describes the characteristics of the MISS learning curve and discusses how to manage these unique complications.

2 The Basic Concept of the Minimally Invasive Spine Surgery Minimally invasive surgery involves limited exposure with minimal surgical incisions to reduce tissue traumatization [9–11]. Unlike traditional open surgery, MISS uses a percutaneous or muscle-splitting access with a tubular device that minimizes tissue injury during surgery (Fig. 1). The preservation of normal tissues may result in clinical benefits such as decreased perioperative morbidity, limited blood loss, shorter hospital stay, and earlier return to normal life activities [10, 11]. Small skin incisions with a tubular retractor system or percutaneous instrumentation devices are typically used in MISS techniques.

Y. Ahn (*) Department of Neurosurgery, Gil Medical Center, Gachon University College of Medicine, Incheon, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_3

15

Y. Ahn

16

a

Fig. 1  The basic principle of minimally invasive spine surgery. Percutaneous or muscle-splitting access with a tubular device may minimize tissue injury during surgery

3.1 What Is the Learning Curve? The definition of a learning curve in a surgical procedure is a graphical representation of the time taken and/or the number of procedures an average surgeon needs to be able to perform independently with a reasonable outcome [12]. In 1885, Herman Ebbinghaus first described the concept of a learning curve in the field of the psychology of learning [13]. In 1909, Bryan and Harter first used the term “learning curve,” which represents a diagram plotting the acquisition of a telegraphic language over time [13]. In 1936, Wright described the effect of learning on production costs in the aircraft industry [13]. Based on this idea, a repeated operation takes less time to perform. The learning curve typically consists of three elements: (1) the starting point as the initial case, (2) the learning rate, and (3) asymptote when the “learned” or expert level is reached, and the “learning” can be established at the point at which the learning curve plateaus (Fig. 2) [14, 15]. The familiar expression “a steep learning curve” is still confusing and controversial in terms of terminology. Some authors state that a steep learning curve is desirable [16]. Traditionally, surgery is challenging to learn.

(a). In contrast, the traditional “open” procedure may result in considerable muscle injury and postoperative back pain and disability (b)

Plateau

Performance measure

3 Learning Curve of Minimally Invasive Spine Surgery

b

Learning rate Starting point

Number of trials or attempts at learning Fig. 2  The learning curve typically consists of three components: (1) the starting point as the initial case, (2) the learning rate, and (3) the asymptote or plateau at which the “learned” or expert level is reached

However, a steeper curve represents faster learning progress in a small number of cases, which is the opposite intent of the term [17].

3.2 Cut-Off Point of the Learning Curve One of the essential purposes of learning curve studies is to determine the cut-off point or zone that differentiates between the training (early) or trained (late) stages in a surgeon’s career. The cut-off point can be determined in two ways. First, it may be the asymptote at which the training curve plateaued by the cumulative sum

Learning Curve and Complications of Minimally Invasive Spine Surgery

analysis. Second, it can be selected randomly based on the expert’s experience or the literature review in some studies. A simple dichotomous comparison can be conducted between the early and late groups. Ideally, the asymptote in the curve and group comparison should be demonstrated simultaneously in a learning curve study.

17

3.4 Current Learning Curve Studies of Minimally Invasive Spine Surgery

Most studies evaluated cut-off points based on simple task efficiency, including operative time. However, some studies have also demonstrated the cut-off points for patient outcomes, such as pain score, success rate, and complications. Ideal 3.3 Outcome Measures: Task-­ learning curve studies should focus more on Efficiency Measures vs. patient outcome measures than simple task effiPatient Outcome Measures ciency. Some studies depicted the actual “learning curve” with an asymptote utilizing cumulative In general, there are two categories of outcome sum analysis in terms of methodology. In conmeasures in learning curve studies: (1) task-­ trast, other studies showed results only by dichotefficiency parameters, including operative time, omous comparisons between early and late blood loss, amount of excised tissue, and number groups [18, 22]. The rate of learning progress of hand movements; and (2) patient outcome may be affected by the surgical indications, trainparameters, including global result, pain score, ing status, surgical technique, and outcome meafunctional status, complications, need for revi- sures. Therefore, a careful interpretation is sion surgery, and survival [15, 17, 18]. needed for the learning curve of MISS. The most frequently used outcome measure as a task-efficiency measure is the operative time or duration of surgery [18]. Operative time helps 4 Typical Complications assess the learning progression status objectively Related to Minimally and quantitatively. Therefore, the operative time Invasive Spine Surgery is used as a primary indicator of the learning process in most learning curve studies. Cut-off Minimally invasive surgery is typically perpoints are determined based on operative time in formed using a percutaneous approach with a most studies. Other task-efficiency measures, small tubular retractor under endoscopic or fluoincluding anesthesia time, fluoroscopy time, esti- roscopic guidance. Therefore, unique adverse mated blood loss, and accuracy of screw place- events related to the minimally invasive procement, can also be evaluated. dure may occur under the following conditions. However, the technical level of practical medi- First, a relatively small surgical field may result cine cannot be assessed using only advanced in limited decompression or inadequate tissue task-efficiency parameters. Instead, true mastery manipulation. Second, sophisticated bimanual of the surgical technique can be evaluated using movement may be limited in cases of delicate tispatient outcome measurements [18–21]. The cur- sue dissection, such as dural repair or tissue rently reported cut-off points may be inadequate retraction. Third, unlike three-dimensional vision for patient outcomes for the following reasons. in microscopic surgery, fluoroscopic or endoFirst, outcome measures may be heterogeneous scopically controlled surgery can only provide a and difficult to quantify. Second, more time or two-dimensional image. cases may be required to achieve a plateau in the Typical complications related to MISS are (1) learning process. However, the clinical plateau or incidental durotomy, (2) incomplete neural “learned” level should also be evaluated using decompression, (3) inappropriate instrument outcome measures, including global results, pain positioning, and (4) unusual hematoma or infecscore, complications, and surgical failure. tion [23–25].

Y. Ahn

18

1. Dural tears One of the most critical complications was unexpected dural tear (Fig. 3a). A review revealed that radiculopathy with cerebrospinal fluid (CSF) leakage or dural tear is the most common complication of minimally invasive interbody fusion surgeries [26]. This is also the primary cause of the steep learning curve for MISS.  Inadequate tissue manipulation under limited tubular or endoscopic visualization may cause accidental dural membrane injuries. In water-based endoscopic procedures, dural tears with CSF leakage can be ignored intraoperatively. Unrecognized or overlooked dural tears may cause significant postoperative pain or neurological deficits. Moreover, even if recognized, in situ primary repair is not feasible. Conversion to open surgery is often required in patients with significant dural tears. Fig. 3 Typical complications of minimally invasive spine surgery. (a) Dural tear is the most common and critical adverse event. Note the intraoperative dural tear during the percutaneous endoscopic lumbar discectomy (arrows). (b) Limited surgical exposure may cause incomplete decompression. (c) Inadequate use of percutaneous devices may cause screw malposition. (d) Approach-related complications such as hematoma or infection may occur due to a wrong surgical approach. Note the retroperitoneal hematoma after transforaminal endoscopic lumbar discectomy (arrows)

2. Incomplete decompression A narrow visual field and limited surgical devices can cause incomplete decompression and persistent pain (Fig. 3b) [27]. The anatomical orientation of endoscopic or tubular surgery is significantly different from that of standard open surgery. Therefore, spinal surgeons are unfamiliar with minimal access surgeries. The surgical failure rate due to incomplete decompression was higher, particularly at the beginner stage. 3. Inappropriate instrument positioning Percutaneous pedicle screw fixation is a typical MISS technique. However, percutaneous procedures rely on fluoroscopic visualization without exposure to open tissue. Therefore, spine surgeons cannot check the typical anatomical landmarks during screw insertion. Consequently, screw malposition

a

b

c

d

Learning Curve and Complications of Minimally Invasive Spine Surgery

may be caused by fluoroscopy-controlled instrumentation (Fig. 3c) [28]. 4. Unusual hematoma or infection One of the most peculiar benefits of MISS is the rare occurrence of postoperative bleeding or infections. Less tissue exposure and a muscle-preservation approach can reduce normal tissue damage and subsequent hematoma or infection. However, unusual approach-related bleeding or infections can occur. For example, in transforaminal endoscopic lumbar discectomy, an inadequate transforaminal approach may damage the radicular lumbar artery and cause psoas muscle bleeding or retroperitoneal hematoma (Fig. 3d) [29]. Although uncommon, percutaneous intradiscal decompression procedures can cause postoperative spondylodiscitis or surgical site abscess [30].

4.1 How to Speed Up the Learning Curve and Prevent Complications Typically, standard spine surgeons have little chance of learning minimally invasive procedures during their residency or training period. Therefore, a systematic training course is required to accelerate the learning curve and reduce complications. The typical training program consists of the following elements: (1) conceptual lectures with operative videos, (2) hands-on workshops with a dummy, (3) cadaver workshops, and (4) bedside practice supervised by a senior surgeon in actual cases [18, 22]. Before a particular learning course, extensive training in conventional open or microscopic surgery is mandatory for effective learning of the minimally invasive technique because it can provide the trainee with the primary senses of neurovascular and musculoskeletal tissues. The development of new technologies can facilitate the procedure and prevent adverse events. Intraoperative navigation techniques or location methods can increase the accuracy and success rates of surgery. The development of sur-

19

gical devices that specialize in a minimally invasive approach may increase its effectiveness. In addition to technical aspects, appropriate patient selection is essential for mastering the MISS technique. It is recommended that MISS be performed for typical, uncomplicated cases during the beginner period until a learning plateau is reached. After achieving a “learned” level, the surgeon can address more complex issues. A lack of consistency in the surgical indication during the “learning” period will make the technique more complicated.

5 Summary Minimally invasive spine surgery techniques have been developed in several ways: 1. Muscle-preservation approach using tubular retractors. 2. Percutaneous instrumentation under fluoroscopic guidance or navigation systems. 3. Percutaneous epidural or intradiscal therapies modifying adhesive tissues or pain sources. 4. Endoscopic spine surgeries using a working-­ channel endoscope. However, a steep learning curve and approach-­ related complications can lead to surgical failure. Extensive and systematic training courses and technical development should be conducted to overcome these barriers.

References 1. Jaikumar S, Kim DH, Kam AC. History of minimally invasive spine surgery. Neurosurgery. 2002;51(5 Suppl):S1–S14. 2. Fessler RG, O’Toole JE, Eichholz KM, et  al. The development of minimally invasive spine surgery. Neurosurg Clin N Am. 2006;17(4):401–9. 3. Banczerowski P, Czigléczki G, Papp Z, et  al. Minimally invasive spine surgery: systematic review. Neurosurg Rev. 2015;38(1):11–26. 4. Phan K, Rao PJ, Kam AC, Mobbs RJ.  Minimally invasive versus open transforaminal lumbar interbody fusion for treatment of degenerative lumbar disease:

20 systematic review and meta-analysis. Eur Spine J. 2015;24(5):1017–30. 5. Khan NR, Clark AJ, Lee SL, Venable GT, Rossi NB, Foley KT. Surgical outcomes for minimally invasive vs open transforaminal lumbar interbody fusion: an updated systematic review and meta-analysis. Neurosurgery. 2015;77(6):847–74; discussion 874. 6. Virk SS, Yu E.  The top 50 articles on minimally invasive spine surgery. Spine (Phila Pa 1976). 2017;42(7):513–9. 7. Clark AJ, Safaee MM, Khan NR, et  al. Tubular microdiscectomy: techniques, complication avoidance, and review of the literature. Neurosurg Focus. 2017;43(2):E7. 8. Vaishnav AS, Othman YA, Virk SS, et al. Current state of minimally invasive spine surgery. J Spine Surg. 2019;5(Suppl 1):S2–S10. 9. Derman PB, Phillips FM.  Complication avoidance in minimally invasive spinal surgery. J Spine Surg. 2019;5(Suppl 1):S57–67. 10. Weiss H, Garcia RM, Hopkins B, Shlobin N, Dahdaleh NS. A systematic review of complications following minimally invasive spine surgery including transforaminal lumbar interbody fusion. Curr Rev Musculoskelet Med. 2019;12(3):328–39. 11. Ahn Y. Devices for minimally-invasive microdiscectomy: current status and future prospects. Expert Rev Med Devices. 2020;17(2):131–8. 12. Subramonian K, Muir G. The ‘learning curve’ in surgery: what is it, how do we measure it and can we influence it? BJU Int. 2004;93(9):1173–4. 13. Bach C, Miernik A, Schönthaler M. Training in robotics: the learning curve and contemporary concepts in training. Arab J Urol. 2014;12(1):58–61. 14. Cook JA, Ramsay CR, Fayers P. Statistical evaluation of learning curve effects in surgical trials. Clin Trials. 2004;1(5):421–7. 15. Ramsay CR, Grant AM, Wallace SA, Garthwaite PH, Monk AF, Russell IT.  Assessment of the learning curve in health technologies. A systematic review. Int J Technol Assess Health Care. 2000;16(4):1095–108. 16. Benzel EC, Orr RD. A steep learning curve is a good thing! Spine J. 2011;11(2):131–2. 17. Hoppe DJ, de Sa D, Simunovic N, Bhandari M, Safran MR, Larson CM, Ayeni OR.  The learning curve for hip arthroscopy: a systematic review. Arthroscopy. 2014;30(3):389–97. 18. Ahn Y, Lee S, Son S, Kim H, Kim JE. Learning curve for transforaminal percutaneous endoscopic lumbar discectomy: a systematic review. World Neurosurg. 2020;143:471–9.

Y. Ahn 19. Sánchez-Santos R, Estévez S, Tomé C, González S, Brox A, Nicolás R, Crego R, Piñón M, Masdevall C, Torres A. Training programs influence in the learning curve of laparoscopic gastric bypass for morbid obesity: a systematic review. Obes Surg. 2012;22:34–41. 20. Sclafani JA, Kim CW. Complications associated with the initial learning curve of minimally invasive spine surgery: a systematic review. Clin Orthop Relat Res. 2014;472:1711–7. 21. Simonson DC, Roukis TS. Incidence of complications during the surgeon learning curve period for primary total ankle replacement: a systematic review. Clin Podiatr Med Surg. 2015;32:473–82. 22. Ahn Y, Lee S, Son S, Kim H. Learning curve for interlaminar endoscopic lumbar discectomy: a systematic review. World Neurosurg. 2021;150:93–100. 23. Maroon JC.  Current concepts in minimally invasive discectomy. Neurosurgery. 2002;51(5 Suppl):S137–45. 24. Perez-Cruet MJ, Fessler RG, Perin NI.  Review: complications of minimally invasive spinal surgery. Neurosurgery. 2002;51(5 Suppl):S26–36. 25. Nerland US, Jakola AS, Solheim O, et al. Minimally invasive decompression versus open laminectomy for central stenosis of the lumbar spine: pragmatic comparative effectiveness study. BMJ. 2015;350:h1603. 26. Karikari IO, Isaacs RE.  Minimally invasive transforaminal lumbar interbody fusion: a review of techniques and outcomes. Spine (Phila Pa 1976). 2010;35(26 Suppl):S294–301. 27. Heemskerk JL, Oluwadara Akinduro O, Clifton W, Quiñones-Hinojosa A, Abode-Iyamah KO.  Long-­ term clinical outcome of minimally invasive versus open single-level transforaminal lumbar interbody fusion for degenerative lumbar diseases: a meta-­ analysis. Spine J. 2021;21(12):2049–65. 28. El-Desouky A, Silva PS, Ferreira A, Wibawa GA, Vaz R, Pereira P. How accurate is fluoroscopy-guided percutaneous pedicle screw placement in minimally invasive TLIF? Clin Neurol Neurosurg. 2021;205:106623. 29. Ahn Y, Kim JU, Lee BH, Lee SH, Park JD, Hong DH, Lee JH.  Postoperative retroperitoneal hematoma following transforaminal percutaneous endoscopic lumbar discectomy. J Neurosurg Spine. 2009;10(6):595–602. 30. Ahn Y, Lee SH.  Postoperative spondylodiscitis following transforaminal percutaneous endoscopic lumbar discectomy: clinical characteristics and preventive strategies. Br J Neurosurg. 2012;26(4):482–6.

Part II Endoscopic Spine Surgery

History and Basic Concepts of Full-­Endoscopic Spine Surgery Sang Gu Lee

1 Introduction The main existing surgical technique for lumbar radiculopathy due to lumbar disc herniation (LDH) is open microdiscectomy. Surgical treatment of lumbar disc disease has been a challenge for spinal surgeons since it was first reported by Dandy [1] in 1929. In 1934, Mixter and Barr [2] published the first surgical treatment of intervertebral disc pathology, often described as low back pain or sciatica. Discectomy surgery under a microscope was performed by Yasargil [3] and Caspar [4] in 1977. Spinal disc surgery under a surgical microscope allows the prolapsed disc to be removed accurately and safely, avoiding many neurological complications. Although spine surgery has developed rapidly after the introduction of microdiscectomy, various postoperative complications appear as the human lifespan increases, requiring additional surgical procedures. Minimally invasive spine surgery has been playing a major role in reducing peri- and postoperative morbidities associated with spine surgery. Endoscopic spine surgery is a principal field of minimally invasive spine surgery. In the early days of endoscopic spine surgery, many spine surgeons were shunned due to the S. G. Lee (*) Department of Neurosurgery, Gachon University, Gil Medical Center, Incheon, Republic of Korea e-mail: [email protected]

poor equipment and low resolution of the endoscope. However, advancements and development in optical technology and microsurgical equipment have made endoscopic procedures more approachable with promising surgical outcomes. In the future, endoscopic spinal surgery is expected to play a leading role in the field of robotic-assisted spinal surgery.

2 History of Full-Endoscopic Spine Surgery 2.1 Foundation of Endoscopic Spine Surgery In 1964, Lyman Smith [5] published a paper about enzymatic dissolution of the nucleus pulposus, a procedure which he called chemo-­ nucleolysis. It was known at that time that an enzyme called Chymopapain, which was derived from the papaya plant, was able to hydrolyze proteoglycans. In the 1980s, this procedure became popular as a minimally invasive technique for treating a herniated lumbar disc. The long-term prognosis was good, complications were rare, and chemo-nucleolysis appeared to be an alternative to discectomy. However, the procedure gradually disappeared due to the appearance of rare but serious side effects. Perhaps this procedure was the beginning of percutaneous minimally invasive spine surgery.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_4

23

24

Fig. 1  Parviz Kambin

S. G. Lee

was performed indirectly. The next step in the advancement of the percutaneous discectomy technique was the addition of the endoscope. The first reported introduction of a modified arthroscope into the intervertebral disc space was reported by Forst and Hausman [8] in 1983, and the first endoscopic views of a herniated nucleus pulposus were published by Kambin et al. [9, 10] in 1988. In 1990, Kambin [11] introduced the anatomical transforaminal approach and triangular safe zone. It was the “Kambin’s triangle” (Fig.  2) which reminds us of his pioneering work in full-­ endoscopic spine surgery.

2.2 First Generation of Endoscopic Spine Surgery

Fig. 2  Kambin’s triangle; Illustration of three anatomical barriers. Sympathetic trunk and ganglia (a), exiting nerve and ganglia (b), traversing nerve (c), and sinuvertebral nerves (d)

The concept of endoscopic spinal surgery was initially based on percutaneous discectomy. A technique for percutaneous non-visualized indirect spinal canal decompression—percutaneous discectomy—through a posterolateral approach was described by Parviz Kambin [6] (Fig.  1) in 1973 and Hijikata et al. [7] in 1975. However, the removal of the disc was not under direct visualization and therefore the decompression procedure

The first-generation endoscopic spine surgery can be summarized as percutaneous endoscopic spine surgery. Percutaneous endoscopic lumbar disc resection was introduced by Mayer [12] in 1993. A full-scale endoscopic, minimally invasive disc surgery using the Yeung Endoscopy Spine System (YESS) developed by Anthony T. Yeung [13] (Fig. 3) was introduced soon after in 1999. This method replaces the traditional indirect percutaneous endoscopic procedure. The YESS at this time was based on the inside-­ out approach which had limited surgical indications. Epidural approach was attempted to address the limitations of the transforaminal approach which initially targeted the intradiscal space, but early endoscopic spinal surgery was limited by poor surgical exposure and instruments. The Outside-in approach was first introduced by Schubert and Hoogland [14], which expanded the range of surgical indications for the transforaminal approach. Through the transforaminal approach, several techniques such as outside-in, inside-out, and mobile outside-in techniques were modified and applied to different lumbar pathologies [15, 16]. Surgical techniques have also improved with new technological developments.

History and Basic Concepts of Full-Endoscopic Spine Surgery

25

2.4 Third Generation of Endoscopic Spine Surgery In the third generation, the paradigm has shifted from endoscopic discectomy to endoscopic decompression. Endoscopic lumbar decompression for spinal stenosis is the most representative. Previously, spinal stenosis was a contraindication for endoscopic spinal surgery [18]. With the further development of high-­ resolution endoscopic technology and various cutting equipment, spinal endoscopic surgery is now becoming a popular surgery for spinal stenosis. Many papers related to this have been published by Choi [19], Ahn [20], and Kim [21]. Endoscopic decompression allows sufficient decompression for spinal stenosis with minimal laminectomy, minimal muscle damage, and minimal neuromuscular traction [22].

Fig. 3  Anthony T. Yeung

2.3 Second Generation of Endoscopic Spine Surgery The second generation of endoscopic spine surgery began with the introduction of interlaminar endoscopic spine surgery. A laminectomy and discectomy performed through an interlaminar approach is referred to as interlaminar endoscopic lumbar discectomy. For this reason, an interlaminar endoscopic lumbar discectomy was initially not included in the mainstream of endoscopic spine surgery and was considered an advanced type of microscopic lumbar discectomy. In the early 2000s, German spinal surgeon Sebastian Rütten [17] described this technique and applied it to an interlaminar endoscopic approach. This has greatly expanded the versatility of this technology.

2.5 Fourth Generation of Endoscopic Spine Surgery Perhaps the fourth generation of endoscopic spine surgery will be summarized as the intervertebral fusion or endoscopic intervertebral fusion technique. Spinal fusion has been performed as a treatment for various spinal diseases and is one of the most important treatments for maintaining stability. Conventional open fusion surgery provides rigid stabilization to the pathologic spine and is associated with extensive decompression of the neural structures and extensive damage to the posterior spinal anatomical structures. Open fusion requires a long recovery period and is associated with many morbidities. Recently, to solve this problem, interbody fusion using an endoscopic technique has been reported [23]. Thanks to recent advances in surgical equipment, spinal interbody fusion can now be performed through endoscopic spinal surgery. However, fusion surgery using the endoscopic

26

technique has not yet been popularized due to the lack of sufficient follow-up period and long learning curve. Nevertheless, attempts to solve these problems are ongoing and require more ­evidence [24]. Furthermore, the goal of endoscopic spine surgery is also to enable roboticassisted spine surgery using the navigation system.

3 Basic Concepts of Full-­ Endoscopic Spine Surgery

S. G. Lee

of the surgical techniques and solve the biomechanics involved, many modern engineering equipments must be further developed in the field of surgery. In the not-too-distant future, artificial intelligence-­based medicine, high-resolution 3D endoscopy systems, safe bone resection equipment, and navigation systems will surely be developed. Instrument fixation using robotic-­assisted systems and advanced graft material will ensure biological bone fusion. With such technology in hand, endoscopic spine surgery will truly become the core of minimally invasive spine surgery.

Regarding the lumbar spine, there are two approaches to full-endoscopic discectomy: transforaminal and interlaminar. Transforaminal full-­ References endoscopic lumbar discectomy has been developed as a representative endoscopic spine 1. Dandy WE.  Loose cartilage from intervertebral disk surgery. Although the terminology used to simulating tumor of the spinal cord. Arch Surg. 1929;19:660–72. describe this technique is varied, the AOSpine 2. Mixter WJ, Barr JS. Rupture of the intervertebral disc group proposed the unified term “transforaminal with involvement of the spinal canal. N Engl J Med. endoscopic lumbar discectomy”(TELD) [25]. 1934;211:210–5. The basic concepts of full-endoscopic spine 3. Yasargil MG. Microsurgical operations for herniated lumbar disc. Adv Neurosurg. 1977;4:81–2. surgery can be described as follows. First, the 4. Caspar W. A new surgical procedure for lumbar disc transforaminal endoscopic system should be herniation causing less tissue damage through a microplaced as close to the target point as possible, surgical approach. Adv Neurosurg. 1977;4:74–80. while avoiding exiting nerve root irritation. 5. Smith L.  Enzyme dissolution of the nucleus pulposus in humans. J Am Med Assoc. 1964;187(2): Second, selective removal of the herniated disc 137–40. fragments after sufficiently releasing the annular 6. Kambin P, Gellman H.  Percutaneous lateral discecanchorage points is essential to avoid incomplete tomy of the lumbar spine. A preliminary report. Clin decompression and to prevent an early recurOrthop. 1983;174:127–32. 7. Hijikata S. A method of percutaneous nuclear extracrence. Third, the endpoint of the procedure can tion. J Toden Hosp. 1975;5:39–42. be determined when solid dural pulsation and 8. Forst R, Hausmann B.  Nucleoscopy—a new examifree mobilization of the nerve root are observed. nation technique. Arch Orthop Trauma Surg. Finally, surgeons should always ensure that the 1983;101:219–21. 9. Kambin P, Nixon JE, Chait A, Schaffer JL. Annular anatomical layers are discriminated between the protrusion: pathophysiology and roentgenographic neural tissue and disc material during the proceappearance. Spine (Phila Pa 1976). 1988;13:671–5. dure [26]. 10. Kambin P, Sampson S.  Posterolateral percutaneous

4 Summary Endoscopic spine surgery is not a common operation that any spine surgeon can easily perform. Endoscopic spine surgery is known for its steep learning curve and requires a comprehensive understanding of the biomechanics and anatomy of the spine. In addition, to increase the accuracy

suction-excision of herniated lumbar intervertebral discs. Report of interim results. Clin Orthop Relat Res. 1986;207:37–43. 11. Kambin P, editor. Arthroscopic microdiscectomy: minimal intervention spinal surgery. Baltimore, MD: Urban & Schwarzenberg; 1990. 12. Mayer HM, Brock M.  Percutaneous endoscopic lumbar discectomy (PELD). Neurosurg Rev. 1993;16:115–20. 13. Yeung AT.  Minimally invasive disc surgery with the Yeung Endoscopic Spine System (YESS). Surg Technol Int. 1999;8:267–77.

History and Basic Concepts of Full-Endoscopic Spine Surgery 14. Schubert M, Hoogland T.  Endoscopic transforaminal nucleotomy with foraminoplasty for lumbar disk herniation. Oper Orthop Traumatol. 2005;17:641–61. 15. Kim HS, Paudel B, Jang JS, et al. Percutaneous endoscopic lumbar discectomy for all types of lumbar disc herniations (LDH) including severely difficult and extremely difficult LDH cases. Pain Physician. 2018;21:E401–8. 16. Choi G, Lee SH, Lokhande P, et  al. Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique using rigid working channel endoscope. Spine (Phila Pa 1976). 2008;33:E508–15. 17. Rütten S, Komp M, Merk H, Godolias G.  Surgical treatment for lumbar lateral recess stenosis with the full-endoscopic interlaminar approach versus conventional microsurgical technique: a prospective, randomized, controlled study. J Neurosurg Spine. 2009;10(5):476–85. 18. Dezawa A, Sairyo K. New minimally invasive discectomy technique through the interlaminar space using a percutaneous endoscope. Asian J Endosc Surg. 2011;4:94–8. 19. Choi I, Ahn JO, So WS, et  al. Exiting root injury in transforaminal endoscopic discectomy: preop-

27

erative image considerations for safety. Eur Spine J. 2013;22:2481–7. 20. Ahn Y. Transforaminal percutaneous endoscopic lumbar discectomy: technical tips to prevent complications. Expert Rev Med Devices. 2012;9:361–6. 21. Kim HS, Adsul N, Kapoor A, et al. A mobile outside­in technique of transforaminal lumbar endoscopy for lumbar disc herniations. J Vis Exp. 2018;(138):57999. 22. Ahn Y.  Percutaneous endoscopic decompression for lumbar spinal stenosis. Expert Rev Med Devices. 2014;11:605–16. 23. Jacquot F, Gastambide D.  Percutaneous endoscopic transforaminal lumbar interbody fusion: is it worth it? Int Orthop. 2013;37:1507–10. 24. Lee SH, Erken HY, Bae J. Percutaneous transforaminal endoscopic lumbar interbody fusion: clinical and radiological results of mean 46-month follow-up. Biomed Res Int. 2017;2017:3731983. 25. Hofstetter CP, Ahn Y, Choi G, et al. AOSpine consensus paper on nomenclature for working-channel endoscopic spinal procedures. Global Spine J. 2020;10(2 Suppl):111S–21S. 26. Lee SG, Ahn Y.  Transforaminal endoscopic lumbar discectomy: basic concepts and technical keys to clinical success. Int J Spine Surg. 2021;15(Suppl 3):S38–46.

Transforaminal Endoscopic Lumbar Discectomy Yong Ahn

1 Introduction To date, open lumbar microdiscectomy (OLM) is the standard surgical technique for lumbar radiculopathy that results from lumbar disc herniation (LDH) [1–6]. This technique provides excellent and reliable outcomes and has gained popularity among spine surgeons. However, some adverse effects, including wide muscle opening, facet injury, and excessive neural retraction, may result in long-term sequelae by affecting the normal tissues. Since Kambin [7] and Hijikata [8] independently developed posterolateral percutaneous lumbar discectomy; the transforaminal endoscopic lumbar discectomy (TELD) technique was developed as an effective surgical alternative to the open microdiscectomy [9, 10]. Conceptually, selective discectomy can be performed under full-endoscopic visualization through the foraminal keyhole while bypassing the posterior healthy tissues, and the clinical outcomes are comparable in terms of superior postoperative recovery time and quality of life. Therefore, the application of endoscopic spine surgery is rapidly increasing in the worldwide spine society [11, 12]. However, the long learning curve and rarity of appropriate training Y. Ahn (*) Department of Neurosurgery, Gil Medical Center, Gachon University College of Medicine, Incheon, Republic of Korea

courses for beginners have made the procedure difficult or unfamiliar to spine surgeons. Moreover, there is a lack of practical guidance regarding the technical pitfalls associated with various LDH types, including contained, extruded, migrated, and recurrent LDH, affecting the different disc levels and zones. The objectives of this review were to describe the detailed techniques used to achieve relevant outcomes and avoid adverse events. This article will help beginner spine surgeons learn the TELD technique and apply it to different LDH cases in clinical practice.

1.1 Basic Principle The primary concept of TELD is “bypassing” the healthy tissues. A posterolateral percutaneous endoscopic approach through the foraminal window may directly access the pathological disc while preserving the posterior normal musculoskeletal structures (Fig.  1). Conventional open microdiscectomy inevitably violates typical posterior structures, such as the paraspinal muscle, laminar bone with facet, and dural sac, to expose the herniated disc. As a result, substantial muscle atrophy and neural sequelae may persist despite the successful resolution of radiculopathy after open surgery. However, the foraminal keyhole may provide a direct posterolateral route to disc pathology, while avoiding normal tissues.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_5

29

Y. Ahn

30

Fig. 1  The principle of transforaminal endoscopic lumbar discectomy (TELD). A direct percutaneous approach to the target lesion bypassing the posterior musculoskeletal structures can be feasible through a foraminal window. A selective discectomy can then be performed under endoscopic visualization

Therefore, TELD may result in better outcomes and rapid recovery without long-term surgical sequelae [13–15].

1.2 Nomenclature There are several categories of endoscopic spine surgery (ESS) on the basis of the type of endoscope used: percutaneous endoscopic (or full-­ endoscopic), biportal endoscopic, microendoscopic, laparoscopic (or thoracoscopic), and epiduroscopic [16–19]. Transforaminal percutaneous endoscopic lumbar discectomy (PELD) is the most commonly used technique. The names of PELD-like methods have varied according to the author’s preference. Recently, the AO spine group presented a unified name: transforaminal endoscopic lumbar discectomy (TELD) [20]. The TELD technique has the following characteristics: (1) use of a working channel endoscope with an optic system and a working channel in a thin tubular device; (2) a complete percutaneous approach with a stab skin wound; and (3) usually monoportal work with constant saline irrigation [18].

1.3 Evidence Over a 40-year history of endoscopic spine surgery, the TELD technique has been most commonly discussed and verified by investigators, especially in scientific articles reporting level I/II studies.

Some pioneer surgeons have reported the effectiveness of the TELD technique compared to open surgery in randomized controlled trials [21–27]. Mayer and Brock [23] compared the clinical outcomes of TELD for LDH with those of open microdiscectomy. They revealed that TELD is an excellent alternative to open surgery in selected patients. Hermantin et al. [21] showed that TELD resulted in less postoperative disability and narcotic requirement than open lumbar discectomy, with equal patient satisfaction. Ruetten et al. [24, 25] demonstrated a full-endoscopic transforaminal discectomy technique and concluded that the results of full-endoscopic surgery were equal to those of conventional discectomy, with the benefits of minimal tissue traumatization. Gibson et al. [27] evaluated the postoperative functional outcomes and perioperative data between the TELD and microdiscectomy groups. The surgical results were similar, with a higher revision rate and more rapid recovery in the TELD group. Recently published systematic reviews with meta-analyses concluded that the TELD technique is equal to or superior to standard open discectomy in terms of clinical effectiveness and minimal invasiveness [28–36]. However, we still require more independent, high-quality RCT with sufficient sample sizes to evaluate various clinical measures, including cost-effectiveness, in the long-term follow-up period.

1.4 Barriers to Entry to the Endoscopic Spine Surgery Despite the benefits of minimal invasiveness and early recovery, the application of ESS in actual practice poses two significant challenges which are as follows: (1) a steep learning curve and (2) limitations in surgical indications. By overcoming the learning curve and widening the indications in the future, the practical application of ESS will become well-known.

Transforaminal Endoscopic Lumbar Discectomy

1.5 Overcoming the Learning Curve One of the main challenges in the clinical application of ESS is its long and arduous learning curve. The reported cut-off points indicating technical proficiency of TELD are variable with a mean value of 24.70 ± 18.99 cases (range, 10–72) [37]. Morgenstern et al. [38] demonstrated that at least 72 instances are needed to achieve excellent outcomes in 90% of surgical cases. We do not think that the reported value indicates that a surgeon becomes an expert in TELD; instead, it means the required learning level that the surgeon can meet with minimum qualifications. The learning curve may be ongoing after this first cut-­ off point because a novel technique is continuously being developed to increase effectiveness. A well-organized training program, including conceptual lessons, hands-on training on a dummy or virtual reality models, cadaver workshops, and learning as an assistant surgeon in actual surgery, is essential to speed up the learning process. In short, the learning process of an aspiring endoscopic surgeon is a journey to manage dural risk while achieving sufficient neural decompression. Dural tear is the most significant adverse event that may cause neurological deficits, sustained pain, and CSF leakage. In the early phase of the learning process, the risk of dural tear was high because of technical proficiency. In the advanced phase however the dural risk may ironically increase when the surgeon pursues thorough decompression. Therefore, great care is mandatory to prevent and manage dural risk regardless of the carrier or experience in ESS.

2 Indications In the early era of ESS, TELD for complex but common LDH cases, including migrated, high canal compromising, calcified, and LDH at the L5– S1 level with a high iliac crest, was contraindicated. The range of applications for TELD was very narrow; however, owing to the remarkable developments in surgical approaches and instruments, the

31

ESS application is now recognized in clinical practice. Currently, endoscopic surgeons can treat most cases of radiculopathy with LDH using TELD. Currently accepted surgical indications for TELD are as follows: Basic Indications 1. Soft LDH causing intractable lumbar radiculopathy 2. Compatible radiographic findings in MRI and CT scan Extended Indications 1. LDH with lateral recess syndrome 2. Migrated, recurrent, partially calcified LDH 3. Discogenic back pain with LDH Contraindications for TELD include the presence of severe central stenosis, segmental instability, infection, or neoplasm, LDH at the L5–S1 level with a high iliac crest.

3 Step-by-Step Technique The standard surgical technique consists of two parts: (1) fluoroscopic-guided percutaneous transforaminal approach and (2) selective discectomy and epidural decompression under working channel endoscope control [10, 13]. After adequate premedication with midazolam (0.05  mg/kg, intramuscularly) and Fentanyl (0.8  μg/kg, intravenously), the patient is positioned prone on a radiolucent table and kept in conscious sedation status. Surgeons can determine skin entry based on preoperative MRI and intraoperative fluoroscopic imaging. Thereafter, an approach needle is inserted posterolaterally into the disc surface through the foraminal window. An epidurogram with contrast media and 1% lidocaine can secure a safe landing for the devices used in the surgery. Then, a discogram with a mixture of indigo carmine and contrast media (1:6 mL) is performed to stain any pathological nucleus blue, which facilitates precise selective discectomy while protecting the neural tissues. A guidewire replaces the approaching needle, and a stab skin wound is created to

Y. Ahn

32

f­ acilitate the insertion of a serial dilator. A bevelended working sheath is placed over the obturator after introducing the final obturator into the disc space. During this process, the surgeon checks the patient’s response to pain or neurological signs. If any, the devices should be withdrawn, and the approach should be restarted from the beginning (Fig. 2).

After the working sheath is settled in the disc, an ellipsoidal working channel endoscope is inserted. The initial endoscopic view includes a stained disc, epidural fat, and soft tissues. The surgical field is then cleaned using a flexible radiofrequency (RF) tip, and the position of the working sheath is adjusted until the anatomical orientation is confirmed. The anatomical strata

a

b

c

d

Fig. 2  Fluoroscopic-­guided percutaneous transforaminal approach. An approach needle is inserted posterolaterally into the disc surface through the foraminal window (a, b).

Finally, a bevel-ended working sheath is placed over the serial obturators (c, d)

Transforaminal Endoscopic Lumbar Discectomy

include the ligamentum flavum, epidural fat, dural sac, entrapped nerve root, the posterior longitudinal ligament, congested annulus pulposus, and disc space (Fig. 3a). The disc fragment herniates from the maternal disc into the epidural space through an annular fissure. The dural sac and nerve root are usually compressed and adhere to the herniated disc fragments. For successful discectomy, sufficient release of annular anchorage is mandatory before discectomy. As the posterior longitudinal ligament and the outer layer of the annulus are cut using endoscopic instruments, the stalk of the herniated disc becomes exposed and mobilized. At the same time, careful dissection between the disc and neural tissues can help separate the herniated disc (Fig.  3b, c). The released and mobilized fragments are removed using micro-forceps and supplementary devices (Fig.  3d). The full-scale selective discectomy process can proceed with a broad movement of the working sheath and endo-

33

scope. The main benefit of the transforaminal endoscopic approach is the excellent flexibility of the endoscopic angle and visual field [10, 39]. Therefore, surgeons can widely decompress the epidural space along the torn annulus. The release-and-removal process can proceed until the herniated disc fragment is sufficiently removed, and the neural tissues are completely decomposed. The surgical endpoint is achieved by ensuring strong pulsation and mobilization of the neural tissues (Fig. 3e). A small number of remnant disc pieces tightly adherent to the neural membrane may be left if the endpoint is secured. An excessive attempt to dissect the remnant fragment of the membrane can cause an unexpected dural tear, which is a critical complication. After confirming the endpoint, the endoscope is removed using a subcutaneous suture and sterile dressing. Patients should be observed for adverse events for several hours before discharge.

b

a

d

Fig. 3  Endoscopic view of the selective endoscopic discectomy. (a) Identification of the anatomical layers in the early view is essential for selective discectomy. Epidural dissection (b) and annular release (c) can isolate the herniated disc fragments. The surgeon should remove not just

c

e

the tip but the entire herniated fragment (d) to prevent incomplete decompression. Strong neural pulsation may indicate the appropriate endpoint of the procedure (e). Note the decompressed traversing nerve root (n), annulus (a), and maternal disc (d)

Y. Ahn

34

a

Fig. 4 Target-oriented transforaminal approach. The landing should be as near to the lesion as possible, and the exiting nerve root in the way of the access route should be preserved. (a) A more horizontal approach to the medial

b

pedicular point is required for central or subarticular lumbar disc herniation (LDH). (b) A steeper path to the lateral pedicular point is recommended for foraminal or extraforaminal LDH

4 Technical Keys to Success The most critical objective of TELD is selective discectomy with complete decompression of the dural sac and nerve roots. Surgeons may encounter different LDH cases in actual practice. However, regardless of the type of LDH, relevant results can be achieved by the following essential keypoints: 1. Target-oriented transforaminal approach (Fig. 4) 2. Annular release with layer-by-layer dissection (Fig. 5) 3. Selective discectomy, including the whole herniated fragment (Fig. 5) 4. Confirmation of the neural decompression by pulsation of the dural sac

Fig. 5  Anatomical layers of the transforaminal endoscopic approach. The key to success in transforaminal endoscopic lumbar discectomy is to identify the precise anatomical layers, including the neural layer (N), posterior longitudinal ligament (PLL), herniated fragment (H), annular tear (A), and disc (D)

Transforaminal Endoscopic Lumbar Discectomy

35

5 Perioperative Considerations

7 Transforaminal Endoscopic Discectomy for Different Causative pathology should be evaluated preSituations cisely by performing sophisticated neurologic examinations and radiographic studies, preoperatively, such as MRI and CT scans. Selective nerve root block is also recommended to confirm radiculopathy. Postoperatively, the patient’s condition should be assessed, including the pain status, neurological symptoms, and signs. Postoperative imaging studies should be performed to check the ­adequacy of decompression and the presence of adverse events.

6 Dural Risk and Incomplete Decompression The most common complication of TELD is incidental dural tear [40]. Complete tissue dissection and decompression may cause dural injury. Dural tears may be overlooked because the surgical field is typically filled with water. Unrecognized dural tears eventually result in persistent radicular pain and neurological sequelae. Another primary complication of TELD is incomplete decompression. A simple removal of the herniated fragment is not sufficient. The confirmation of dural pulsation and mobilization after discectomy is mandatory for clinical success. Ironically, as the surgeon’s endoscopic skill improves during the learning curve period, the risk of dural tears may increase. The dural risk is inversely proportional to the risk of incomplete decompression. In the case of dural tear, the defect should be managed immediately. If the arachnoid membrane is intact or the defect is minor, intraoperative closure must be performed using sealing materials and glue. If the defect is wide and the nerve root protrudes, conversion to open repair surgery may be required. Most importantly, dural tear must be prevented during PELD at all costs. Therefore, the endpoint of the procedure should not be the total exposure of neural tissue but the recovery of neural pulsation or mobilization, even though it is covered with minor tissue debris.

7.1 Migrated Disc Herniation Migrated LDH is common in clinical practice. As the concept of TELD evolved to selective epidural discectomy, advanced techniques for migrated LDH were developed [41]. First, a direction-oriented transforaminal approach is essential. A caudal-to-cranial access angle is recommended for cranially migrated LDH, whereas for caudally migrated LDH, a cranialto-caudal access angle is recommended [41]. This approach enables adequate pursuit of the herniated disc fragment from the annular fissure to the tip of the mass. Second, a foraminoplastic approach may help expose and remove caudally migrated disc fragments [42]. Third, specialized devices such as navigable or flexible forceps can be used to safely remove remotely migrated disc material [41].

7.2 Recurrent Disc Herniation TELD is an excellent surgical option for the treatment of recurrent LDH, especially for recurrent LDH after open lumbar discectomy or microdiscectomy because it avoids posterior fibrotic tissue adhesions. Therefore, the risk of dural tear or neural injury may be minimized while the surgeon can selectively remove the herniated disc fragment. Furthermore, the piece cannot move far away from the annular fissure and is confined by the thick fibrotic capsule formed by a previous surgical scar. Some authors have reported favorable results with TELD for recurrent LDH [13, 43].

7.3 Foraminal/Extraforaminal Disc Herniation The transforaminal approach for foraminal or extraforaminal LDH may be more challenging because the foraminal landing zone is already narrowed and is complicated by the herniated

Y. Ahn

36

disc. Therefore, a modified technique is required in the operative procedure. First, the access angle should be steeper than usual to ensure an adequate surgical field for the foraminal decompression. Second, the foraminal landing point should be as far from the inflamed exiting nerve root as possible [13, 39]. Sometimes, the outside-to-­ inside approach, called the extraforaminal method or floating technique, may be helpful. Third, decompression should be directed from the dorso-caudal aspect of the foramen to the ventral-cranial part. Thus, surgeons can prevent exiting nerve root injuries during discectomy. Finally, to ensure sufficient decompression, full-­ scale foraminal decompression from the axillary zone to the lateral exit zone should be confirmed in the final step of the procedure.

7.4 Upper Lumbar Level Disc Herniation Upper lumbar disc herniation has been reported in more than 5% of all LDH cases [44]. The surgical outcomes of conventional surgery for upper lumbar disc herniation may be less favorable than those for lower lumbar herniations. Small spinal canals and large dural sacs with compact neural tissues may cause neural injury during dural sac retraction or discectomy. TELD may be effective for upper lumbar lesions because the surgeon can remove the extruded disc without extensive dural sac manipulation. Moreover, the foraminal window was sufficiently large for the transforaminal endoscopic approach at the upper level. However, the access method of TELD for the upper lumbar level should be adjusted because of its unique anatomical characteristics: the disc surface is more concave and the dural sac is usually exposed through the foraminal window. Therefore, a steeper approach angle and more lateral landing point in the axial plane are essential for safe and effective decompression.

7.5 Disc Herniation at the L5–S1 Level The L5–S1 disc level has unique anatomical features, including a high iliac crest, small forami-

nal size, bulky facet joint, and inclination of the disc space. Therefore, the transforaminal approach at the L5–S1 level may be challenging. Owing to anatomical limitations, the surgeon has difficulty placing the working sheath correctly and levering the endoscope freely during the procedure at the L5–S1 level [45]. However, many authors could not give up the benefits of the transforaminal approach and developed several tips to overcome the anatomical barriers at the L5–S1 level. The modification of the approach is mainly dependent on the height of the iliac crest and foraminal size [45]. If the highest point of the iliac crest is below the midpedicular line of the L5 vertebra, the conventional transforaminal approach is feasible. In this situation, the surgeon can perform the standard TELD technique. However, when the height of the iliac crest is higher than the mid-­pedicular level of L5, a specialized course may be required. First, the transiliac approach can be helpful in reaching the pathological disc through the foraminal window [46, 47]. Second, a foraminoplastic approach can be another solution to overcome the high iliac crest and narrowed foramen at the L5–S1 level. Resection of part of the facet joint or pedicle may be helpful for the surgeon to expose and reach the epidurally herniated disc using the transforaminal approach. The extent of bone resection was determined on the basis of the LDH zone.

8 Summary Over 45 years of history, TELD has been a representative icon for endoscopic spine surgery and was developed as a bypass surgery that directly approaches the pathology through the foraminal window, preserving the posterior musculoskeletal structures. Currently, targeted epidural fragmentectomy is feasible in most LDH cases. Many randomized controlled trials and meta-analyses have proven their clinical effectiveness. However, the learning curve and the associated complications may be barriers in this minimally invasive procedure. Careful technical considerations and training programs should be implemented to overcome these problems.

Transforaminal Endoscopic Lumbar Discectomy

Conflicts of Interest  None. Financial Disclosure  This study did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

References 1. Silvers HR.  Microsurgical versus standard lumbar discectomy. Neurosurgery. 1988;22(5):837–41. 2. Kahanovitz N, Viola K, Muculloch J. Limited surgical discectomy and microdiscectomy. A clinical comparison. Spine (Phila Pa 1976). 1989;14(1):79–81. 3. Caspar W, Campbell B, Barbier DD, Kretschmmer R, Gotfried Y.  The Caspar microsurgical discectomy and comparison with a conventional standard lumbar disc procedure. Neurosurgery. 1991;28(1):78–86. 4. Papavero L, Caspar W. The lumbar microdiscectomy. Acta Orthop Scand Suppl. 1993;251:34–7. 5. Porchet F, Bartanusz V, Kleinstueck FS, et  al. Microdiscectomy compared with standard discectomy: an old problem revisited with new outcome measures within the framework of a spine surgical registry. Eur Spine J. 2009;18(Suppl 3):360–6. https:// doi.org/10.1007/s00586-­009-­0917-­9. 6. Calikoglu C, Cakir M. Open discectomy vs. microdiscectomy: results from 519 patients operated for lumbar disc herniation. Eurasian J Med. 2018;50(3):178–81. https://doi.org/10.5152/eurasianjmed.2018.18016. 7. Kambin P, Sampson S.  Posterolateral percutaneous suction-excision of herniated lumbar intervertebral discs. Report of interim results. Clin Orthop Relat Res. 1986;207:37–43. 8. Hijikata S. Percutaneous nucleotomy. A new concept technique and 12 years’ experience. Clin Orthop. 1989;238:9–23. 9. Kambin P, O’Brien E, Zhou L, Schaffer JL.  Arthroscopic microdiscectomy and selective fragmentectomy. Clin Orthop Relat Res. 1998;347:150–67. 10. Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar disc herniation: surgical technique, outcome, and complications in 307 consecutive cases. Spine (Phila Pa 1976). 2002;27(7):722–31. 11. Krugluger J, Knahr K.  Minimally invasive disc surgery: a review. Int Orthop. 2001;24(6):303–6. 12. Chang X, Chen B, Li HY, Han XB, Zhou Y, Li CQ. The safety and efficacy of minimally invasive discectomy: a meta-analysis of prospective randomised controlled trials. Int Orthop. 2014;38(6):1225–34. 13. Ahn Y. Transforaminal percutaneous endoscopic lumbar discectomy: technical tips to prevent complications. Expert Rev Med Devices. 2012;9(4):361–6.

37 14. Wang K, Hong X, Zhou BY, et  al. Evaluation of transforaminal endoscopic lumbar discectomy in the treatment of lumbar disc herniation. Int Orthop. 2015;39(8):1599–604. 15. Ahn Y, Lee SG, Son S, Keum HJ. Transforaminal endoscopic lumbar discectomy versus open lumbar microdiscectomy: a comparative cohort study with a 5-year follow-up. Pain Physician. 2019;22(3):295–304. 16. Mayer HM, Brock M.  Percutaneous endoscopic lumbar discectomy (PELD). Neurosurg Rev. 1993;16(2):115–20. 17. Ruetten S, Komp M, Godolias G.  An extreme lateral access for the surgery of lumbar disc herniations inside the spinal canal using the full-endoscopic uniportal transforaminal approach-technique and prospective results of 463 patients. Spine (Phila Pa 1976). 2005;30(22):2570–8. 18. Birkenmaier C, Komp M, Leu HF, Wegener B, Ruetten S. The current state of endoscopic disc surgery: review of controlled studies comparing full-endoscopic procedures for disc herniations to standard procedures. Pain Physician. 2013;16(4):335–44. 19. Ahn Y. Endoscopic spine discectomy: indications and outcomes. Int Orthop. 2019;43(4):909–16. 20. Hofstetter CP, Ahn Y, Choi G, et al. AOSpine consensus paper on nomenclature for working-channel endoscopic spinal procedures. Global Spine J. 2020;10(2 Suppl):111S–21S. 21. Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am. 1999;81(7):958–65. 22. Hoogland T, Schubert M, Miklitz B, Ramirez A.  Transforaminal posterolateral endoscopic discectomy with or without the combination of a low-­ dose chymopapain: a prospective randomized study in 280 consecutive cases. Spine (Phila Pa 1976). 2006;31(24):E890–7. 23. Mayer HM, Brock M. Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg. 1993;78(2):216–25. 24. Ruetten S, Komp M, Merk H, Godolias G.  Full-­ endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine (Phila Pa 1976). 2008;33(9):931–9. 25. Ruetten S, Komp M, Merk H, Godolias G. Recurrent lumbar disc herniation after conventional discectomy: a prospective, randomized study comparing full-endoscopic interlaminar and transforaminal versus microsurgical revision. J Spinal Disord Tech. 2009;22(2):122–9. 26. Meyer G, Rocha IDDA, Cristante AF, et  al. Percutaneous endoscopic lumbar discectomy versus microdiscectomy for the treatment of lumbar disc herniation: pain, disability, and complication

38 rate-a randomized clinical trial. Int J Spine Surg. 2020;14(1):72–8. 27. Gibson JNA, Subramanian AS, Scott CEH.  A randomised controlled trial of transforaminal endoscopic discectomy vs microdiscectomy. Eur Spine J. 2017;26(3):847–56. 28. Nellensteijn J, Ostelo R, Bartels R, Peul W, van Royen B, van Tulder M.  Transforaminal endoscopic surgery for symptomatic lumbar disc herniations: a systematic review of the literature. Eur Spine J. 2010;19(2):181–204. 29. Cong L, Zhu Y, Tu G.  A meta-analysis of endoscopic discectomy versus open discectomy for symptomatic lumbar disk herniation. Eur Spine J. 2016;25(1):134–43. 30. Li XC, Zhong CF, Deng GB, Liang RW, Huang CM.  Full-endoscopic procedures versus traditional discectomy surgery for discectomy: a systematic review and meta-analysis of current global clinical trials. Pain Physician. 2016;19(3):103–18. 31. Ruan W, Feng F, Liu Z, Xie J, Cai L, Ping A.  Comparison of percutaneous endoscopic lumbar discectomy versus open lumbar microdiscectomy for lumbar disc herniation: a meta-analysis. Int J Surg. 2016;31:86–92. 32. Ding W, Yin J, Yan T, Nong L, Xu N.  Metaanalysis of percutaneous transforaminal endoscopic discectomy vs. fenestration discectomy in the treatment of lumbar disc herniation. Orthopade. 2018;47(7):574–84. 33. Zhang B, Liu S, Liu J, et al. Transforaminal endoscopic discectomy versus conventional microdiscectomy for lumbar discherniation: a systematic review and meta-­ analysis. J Orthop Surg Res. 2018;13(1):169. 34. Barber SM, Nakhla J, Konakondla S, et al. Outcomes of endoscopic discectomy compared with open microdiscectomy and tubular microdiscectomy for lumbar disc herniations: a meta-analysis. J Neurosurg Spine. 2019:1– 14. https://doi.org/10.3171/2019.6.SPINE19532. 35. Gadjradj PS, Harhangi BS, Amelink J, et  al. Percutaneous transforaminal endoscopic discectomy versus open microdiscectomy for lumbar disc herniation: a systematic review and meta-analysis. Spine (Phila Pa 1976). 2021;46(8):538–49. 36. Li WS, Yan Q, Cong L.  Comparison of endoscopic discectomy versus non-endoscopic discectomy for symptomatic lumbar disc herniation: a systematic review and meta-analysis. Global Spine J. 2022;12(5):1012–26.

Y. Ahn 37. Ahn Y, Lee S, Son S, Kim H, Kim JE. Learning curve for transforaminal percutaneous endoscopic lumbar discectomy: a systematic review. World Neurosurg. 2020;143:471–9. 38. Morgenstern R, Morgenstern C, Yeung AT. The learning curve in foraminal endoscopic discectomy: experience needed to achieve a 90% success rate. SAS J. 2007;1(3):100–7. 39. Choi I, Ahn JO, So WS, Lee SJ, Choi IJ, Kim H.  Exiting root injury in transforaminal endoscopic discectomy: preoperative image considerations for safety. Eur Spine J. 2013;22(11):2481–7. 40. Ahn Y, Lee HY, Lee SH, Lee JH. Dural tears in percutaneous endoscopic lumbar discectomy. Eur Spine J. 2011;20(1):58–64. 41. Ahn Y, Jang IT, Kim WK.  Transforaminal percutaneous endoscopic lumbar discectomy for very high-grade migrated disc herniation. Clin Neurol Neurosurg. 2016;147:11–7. 42. Choi G, Lee SH, Lokhande P, Kong BJ, Shim CS, Jung B, Kim JS. Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique using rigid working channel endoscope. Spine (Phila Pa 1976). 2008;33(15):E508–15. 43. Ahn Y, Lee SH, Park WM, Lee HY, Shin SW, Kang HY.  Percutaneous endoscopic lumbar discectomy for recurrent disc herniation: surgical technique, outcome, and prognostic factors of 43 consecutive cases. Spine (Phila Pa 1976). 2004;29(16):E326–32. 44. Ahn Y, Lee SH, Lee JH, Kim JU, Liu WC.  Transforaminal percutaneous endoscopic lumbar discectomy for upper lumbar disc herniation: clinical outcome, prognostic factors, and technical consideration. Acta Neurochir (Wien). 2009;151(3):199–206. 45. Choi KC, Park CK. Percutaneous endoscopic lumbar discectomy for L5-S1 disc herniation: consideration of the relation between the iliac crest and L5-S1 disc. Pain Physician. 2016;19(2):E301–8. 46. Osman SG, Marsolais EB.  Endoscopic transiliac approach to L5-S1 disc and foramen. A cadaver study. Spine (Phila Pa 1976). 1997;22(11):1259–63. 47. Choi G, Kim JS, Lokhande P, Lee SH. Percutaneous endoscopic lumbar discectomy by transiliac approach: a case report. Spine (Phila Pa 1976). 2009;34(12):E443–6.

Interlaminar Endoscopic Lumbar Discectomy Gun Choi

1 Introduction The posterior endoscopic approach through the interlaminar space has become one of the most popular approaches for percutaneous Endoscopic procedures. After being reported by Choi et  al. [1] in 2006 in the removal of an intra-canalicular L5– S1 disc herniation, the approach has seen further advancements not only with the development of new equipment and techniques but also many reports of successful outcomes, widening the indications for this procedure. Knowledge of lumbar anatomy is paramount to perform Interlaminar Endoscopic Lumbar Discectomy (IELD), and one must overcome its learning curve.

2 Indications The interlaminar endoscopic lumbar discectomy technique can be used in cases in which adequate access to the disc is difficult through a transforaminal approach due to anatomical and technical reasons. The technique is best suited for the L5–S1 level—due to its unique characteristics and wide interlaminar space—but can also be used in other lumbar levels.

Some of the indications for the use of Interlaminar IELD include: –– Intra-canalicular L5–S1 disc herniation –– Enough interlaminar space to perform the procedure

3 Applied Anatomy Thorough knowledge of anatomy is required in order to safely perform IELD. Surgeons should be aware of defining the herniated disc and its relationship with the surrounding structures.

3.1 Interlaminar Window The shape and size of the interlaminar window are variable, but it is usually larger in lower lumbar levels than in upper lumbar levels. In the lower lumbar spine, the Lamina overhang is smaller, meaning that the extent of the lower margin of the upper lamina over the disc space is smaller (which creates a relatively larger interlaminar space). This overhang decreases as we move to lower lumbar levels, being smallest at the L5–S1 level (3.0–8.5 mm).

G. Choi (*) Woori Hospital, Pohang, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_6

39

G. Choi

40

The maximum interlaminar width, defined as the distance measured between the most inferomedial aspect of the inferior facets, is also greater at L5–S1 (ranging from 21 to 40 mm) due to the relatively wider laminae of L5, which helps on the safe passage of the Working Channel on this level.

3.2 Ligamentum Flavum The ligamentum flavum is a 2–6 mm thick structure that spans over the interlaminar space. It is an active ligament that has an essential biomechanical role and acts as a protective barrier for the thecal sac. It consists of two layers: a superficial layer of loose and obliquely arranged fibers that can be easily detached; and a deep layer, with fibers arranged craniocaudally and attached to the ventral surface of the lamina (Fig. 1). The deep ligamentum flavum merges with the facet capsule in the foraminal region. At the L5–S1 level, the ligament is thinner than in other levels, being the only major protective barrier for neural structures. Removal of this protecting layer during IELD can increase the chance of Peridural fibrosis, as this process occurs from the contact of fibroblasts (derived from the overlying detached muscle) with the spinal canal [2–4].

Upper Level Lamina

Superficial layer

Lower Level Lamina

Deep layer DURAL SAC

Fig. 1  Two layers of the ligamentum flavum superficial layer and deep layer. Traced lines mark the attachment of the deep layer to the ventral surface of the laminae

3.3 Intervertebral Foramen Size Upper lumbar intervertebral foramina tend to be larger than lower lumbar intervertebral foramina.

3.4 Intervertebral Foramen Nerve Root Exit The exit zone of the neural foramen is positioned more medially to the lateral margin of the pedicle on the upper lumbar spine levels, but more laterally in lower levels. The S1 nerve root has a relatively cephalad exit from the thecal sac when compared with the upper lumbar levels. It can exit in line with the level L5–S1 disc space (25%) or above it (75%) [5–8]. Although S1 nerve root take-off angle (the angle in which it leaves the thecal sac) is relatively smaller than that the ones seen on upper lumbar levels, a L5–S1 disc herniation is more likely to be axillary due to its cephalad exit. One should position the herniated disc and set its relationship with the traversing nerve root before IELD. The traversing nerve root exit site from the dural sac should also be carefully accessed preoperatively.

3.5 Herniated Disc Position Herniated discs can be divided into shoulder or axilla-type [7], according to its relative location to the traversing nerve root. For shoulder-type disc herniation, removal of both intradiscal material and prolapse of the nucleus pulposus should be performed through a shoulder approach (lateral to the traversing nerve root) [7]. At the L5–S1 level, this type of herniation is relatively uncommon and needle insertion can be targeted directly over the herniated mass lying over the superomedial aspect of the pedicle.

41

Interlaminar Endoscopic Lumbar Discectomy

For the axilla-type disc herniation, we should understand where the nerve root exits the thecal sac and in relation to the intervertebral disc space. If the traversing nerve root exits the dural sac cephalad or parallel to the intervertebral space, an axillary approach (between the traversing nerve root and dural sac) is advisable to remove both intradiscal and extradiscal fragments [7]. If traversing nerve root exits the dural sac caudal to the intervertebral space, first, an axillary approach should be performed to remove the prolapse of the nucleus pulposus and then a shoulder approach is adopted to remove intradiscal material. On L5–S1 level, axillary disc herniation can displace the S1 nerve root into the subarticular region, creating a potential space between the thecal sac and the nerve root. This artificial space can be explored for carrying out a safe interlaminar endoscopic discectomy.

obtained by following the same conditions as the first image. Once both our C-Arm projections are optimal, markings of our preoperative plan are made on the skin:

4 Step-by-Step Technique

4.2 Anesthesia

4.1 Preoperative Planning

Epidural block + local anesthesia or General anesthesia are suitable for this procedure. We prefer epidural block through the sacral hiatus (caudal block) and local skin infiltration. Local anesthesia can be done by infiltrating the skin and muscle layers with 2% lidocaine (about 5 cc), while 1% lidocaine is used within the epidural space (10 cc with aspiration to avoid injecting it into bloodstream). As IELD is associated with nerve root retraction, which can cause pain for the patient, general anesthesia can be considered. One should bear in mind that the use of general anesthesia takes off the benefit of neural monitoring of a conscious patient.

Anatomic relation between the pathologic disc and surrounding structures are identified with CT and MRI scans and translated into C-Arm images prior to the procedure. Sagittal MRI can give us the extent of downward or upward migration of disc herniation. Axial MRI and CT scans can give us the location of the herniated disc and its relation to the nerve root or thecal sac, along with any deviation of the concerned nerve root. Axial CT will help us to define our entry point with reference to anatomical landmarks. When the patient is adequately positioned on the surgical table, before the start of the surgery, obtaining adequate C-Arm images is a paramount step in following correct pre-op planning. First, a lateral view C-arm image is taken, which should have parallel endplates of the concerned level and should be directed to the midline of the disc. Then, true AP view of the level is

–– Midline is marked, along the tips of the spinous processes of the targeted levels, with no rotation and with the pedicles lying equidistant from the midline. –– The medial pedicular line at the S1 vertebral level was marked on the symptomatic side. –– The superior edge of the cranial lamina and the inferior edge of the caudal lamina were visualized to mark the interlaminar space. –– If neural structures and disc positions are known, they can be marked as well. Further epidurogram can help to precisely determine those structures.

4.3 Positioning and Setting The patient is placed in the prone position on a Wilson frame with minimal abdominal pressure. Skin marking and preoperative planning are revised.

G. Choi

42

m C-Ar r ito Mon

C-Arm

En Vi dos To deo cop e we r

Instrument Table

Anesthetist

Surgeon Nurse

Fig. 2  Schematic display of the surgical room for the IELD procedure

Waterproof surgical drape is applied after local asepsis and scrubbing. Surgeon and scrub nurse with the Mayo trolley stand on the pathologic side of the patient. C-Arm, Video Equipment, and fluid pump are placed on the contralateral side. Anesthesia team stands at the head end of the patient (Fig. 2).

4.4 Discography Discography with indigo carmine dye will serve as a visual asset during our procedure, as the dye colors the acidic degenerative disc material. The relation between the disc and the compressed nerve root will determine the best path to perform the discography. For the axillary type disc herniation, performing discography before surgery through the Kambin’s triangle on a transforaminal approach is safer. On a shoulder-type disc herniation, the needle tip can be safely placed directly on the disc herniation without a great risk of neural injury.

4.5 Target Point and Needle Insertion After the injection of indigo carmine into the disc, our entry point is determined for a correct approach of the herniated disc.

In axilla-type disc herniation, the target point will be located midway between the midline and the medial pedicular line, over the superior edge of the caudal lamina on the AP view (Fig. 3a). On the lateral view, the needle should be targeted just below the superior endplate of the caudal vertebra. A small safe zone for the interlaminar approach was bound medially by the thecal sac, with the traversing root forming the lateral border and the superior edge of the caudal lamina forming the lower border. In case of a shoulder-type herniation, the target was the shoulder of the traversing nerve root and the skin entry point was the most lateral area of the interlaminar space (Fig. 3b). Skin entry point is infiltrated with 2% lidocaine. An 18G spinal needle is inserted towards our safe bony target (Fig. 4). If there is not enough space for needle placement or correct anatomical position is unknown, placing the needle and the cannula superficially to the Ligamentum flavum is advised.

4.6 Epidurogram A useful way to safely determine the trajectory and position of the neural structures and the relation to its surroundings is by performing an epidurogram. After needle insertion to the bony landmark, the needle can be mobilized and placed above the Ligamentum flavum, without trespassing it. The epidural space is then accessed and it gives way after mild resistance; care must be taken not to injure neural structures. Once the position of the needle is confirmed, epidurogram with using the radio-opaque dye is performed and will help determine the neural outline and prevent injury (Fig. 5). After confirmation, epidural block can be administered with 10 cc of 1% lidocaine with aspiration to avoid injecting it into bloodstream, in case a caudal block has not been performed.

43

Interlaminar Endoscopic Lumbar Discectomy

a

Fig. 3 (a) Midline in green, medial pedicular line and pedicles in blue, and target point for the axilla approach in red. (b)

b

Red circle shows the lateral-most portion of the interlaminar window that is targeted in the Shoulder-type disc herniation

Fig. 4 18G Needle insertion and adequate position viewed with C-Arm guidance

Fig. 5  C-Arm AP image of epidurogram performed during IELD procedure. The radiopaque dye shows us the contour of neural structures

44

G. Choi

4.7 Working Channel Establishment Once correct needle placement is achieved, a guidewire is then inserted through the spinal needle (Fig. 6). Once guidewire is inserted, a 7–8  mm stab incision is performed close to the midline from the skin to deep fascia to insert the dilator with ease. The incision should allow us to access the lateral margin of dura, shoulder of traversing nerve root, and subarticular recess without or with minimal bone resection. After skin incision, sequential obturators are passed through the guidewire (Fig.  7). We can palpate and feel interlaminar boundaries and ligamentum flavum with the tip of the obturator. Bone resection prior to ligamentum flavum opening might be needed in case of narrow interlaminar space (this should be planned before surgery). Widening the interlaminar bone window can diminish the volume of intraspinal lavage fluid collection and prevent complications associated with high epidural fluid pressure. Next, our working channel is inserted over the dilator (Figs. 8 and 9) and the endoscope is then placed inside the working sheath (Fig. 10). When working with a round–tip working channel, we should bear in mind that although it is more familiar, its use will require more muscle work, and sometimes it is difficult to find the target point on the ligamentum flavum. If a beveled tip working channel is chosen, firm positioning of the beveled working channel in the V point can decrease the need for muscle work and help in better exposure of ligamentum flavum. Additionally, twisting the beveled tip working channel can help with the removal of the disc herniation and in safe root retraction in the latter stages of the surgery.

Fig. 6  Guidewire is inserted through the needle, and the needle is carefully retrieved

Fig. 7  Insertion of sequential dilators over the guidewire

Fig. 8  (Right): Beveled tip cannula is inserted around dilators and position firmly secured

Interlaminar Endoscopic Lumbar Discectomy

45

Fig. 9  C-Arm images verify correct placement of the beveled tip working channel for a shoulder-type disc herniation at L5–S1 level (Lateral view: Left and AP view: Right). Note that the working channel should be facing medially

scopic scissors. This technique is similar to the conventional microscopic tubular discectomy, being familiar to surgeons. Its disadvantage is the creation of a ligamentum defect from where the chance of epidural fibrosis to occur increases. Care must be taken not to avoid dural tears: surgeons should bear in mind that neural structures are tightly placed inside the canal and when removing the ligamentum flavum, there is the possibility to injure the posteriorly displaced neural structures.

Fig. 10 Endoscope inserted through the working channel

4.8 Ligamentum Flavum Approach Several techniques can be applied when passing through the Ligamentum flavum layer. Understanding its different layers division will help in proper use of those techniques: Ligamentum flavum resection [9]: Underlying ligamentum flavum can be stripped away with the use of punches or endo-

–– Ligamentum flavum splitting [1, 10– 13]: Splitting of the ligamentum flavum can be performed directly with the use of a probe and other surgical instruments (sequential dilators) in endoscopic view and progressive introduction of the working channel through the path created. Another way to perform it is by indirect splitting of the ligament. This is done with the introduction of the guidewire through the ligament, aimed towards the herniated disc fragment; it is followed by the introduction of the obturator and working cannula (Fig. 11). Both techniques present the advantage of spontaneous closure of the ligamentum flavum after removing the working channel, which might help in the prevention of epidural scar tissue.

G. Choi

46

Fig. 11  Endoscopic view of the ligamentum flavum passage through indirect splitting while retrieving the working channel

4.9 Disc Herniation Access The approach to the disc herniation depends on its relation to the traversing nerve root, be it from the shoulder or the axilla. –– Shoulder access Useful for paramedian disc herniation and migrated disc to the lateral recess, in this approach the traversing root position is checked and dissection of the root or lateral margin of the dura from the surrounding inflammatory adhesion is performed with nerve hook and/or a probe. Neural dissection should be done from a more proximal and lateral side of the traversing nerve root in order to prevent neural damage. Medial retraction of neural structures can be safely performed by rotating the beveled-tip cannula (Fig. 12), this is also useful for better exposure of the disc. Axillary access Useful for axilla-type disc herniations, central herniation of L5–S1 level, and central distally migrated fragments. To confirm axillary portion, removal of epidural fat clearly is needed.

Fig. 12  Endoscopic view of the shoulder access where traversing nerve root is in the 10–2 o’clock direction, limited laterally by the pinkish line, while the disc space is limited by the blue lines in the 6–7 o’clock direction

Beveled tip working channel is inserted under endoscopic view between traversing root and dura after dissecting adhesion and proper bleeding control with RF probe. The surgeon can remove axillary fragments and central distal migrated disc without much neural retraction. This approach has a learning curve to it.

4.10 Annulus Approach The annulus can be approached in a couple of different ways: –– Annular resection –– Part of the annulus fibrosus is resected around the protruded area to expose the pathologic disc. –– The approach is familiar, being similar to the conventional technique. Nevertheless, this approach is associated with a high risk of recurrent disc herniation. –– Annular sealing –– Usually, we try to find an existing fissure instead of creating a new one. If creation of fissure is needed to remove the disc, a probe is used to open it. Remove the pathologic disk sufficiently to make certain that

Interlaminar Endoscopic Lumbar Discectomy

47

5.3 Nerve Injury Nerve injuries can be successfully prevented by gentle retraction of the nerve root.

5.4 Vascular Injury Do not perform the discectomy too deeply, to avoid causing a vascular injury. Caution must be used to avoid prevertebral aortic injury, which could be fatal.

5.5 Infection Fig. 13  Endoscopic view of the RF probe sealing the annular defect

there are no disc fragments remaining (Fig. 13). –– Using the RF probe from the distal to the proximal end of the fissure helps on shrinking the size of the bulging disc and sealing the fissure.

5 Complications 5.1 Dural Tear When dural tearing occurs during surgery, it is better to stop the procedure. If the ligamentum flavum is resected to access the spinal canal, care must be taken not to injure the tightly placed dural sac.

5.2 Early Relapse Early relapse after the surgery can be reduced by annular sealing. Sufficient bed rest to allow healing of the surgical field helps to reduce early relapse.

To reduce the chance of postoperative infection, clear surgical fields and infection control measures should be needed (such as the use of antibiotics).

6 Summary Interlaminar endoscopic lumbar discectomy technique is useful in both normal patients and patients with a high iliac crest. The wide range of indications was permitted by the further development of materials and techniques. Knowing the anatomy and the disc relation to neural structures is paramount to perform the procedure safely.

References 1. Choi G, Lee SH, Raiturker PP, Lee S, Chae YS.  Percutaneous endoscopic interlaminar discectomy for intracanalicular disc herniations at L5–S1 using a rigid working channel endoscope. Neurosurgery. 2006;58:ONS59–68. 2. Askar Z, Wardlaw D, Choudhary S, Rege A. A ligamentum flavum-preserving approach to the lumbar spinal canal. Spine. 2003;28(19):E385–90. 3. Aydin Y, Ziyal IM, Duman H, Türkmen CS, Başak M, Sahin Y.  Clinical and radiological results of lumbar microdiskectomy technique with preserving of liga-

48 mentum flavum comparing to the standard microdiskectomy technique. Surg Neurol. 2002;57(1):5–13. 4. Boeree N.  The reduction of peridural fibrosis. In: Gunzburg R, editor. Lumbar disc herniation. Philadelphia, PA: Lippincott Williams & Wilkins; 2002. p. 185–96. 5. Hasegawa T, Mikawa Y, Watanabe R, An HS. Morphometric analysis of the lumbosacral nerve roots and dorsal root ganglia by magnetic resonance imaging. Spine. 1996;21(9):1005–9. 6. Cohen MS, Wall EJ, Brown RA, Rydevik B, Garfin SR. 1990 AcroMed Award in basic science. Cauda equina anatomy. II: extrathecal nerve roots and dorsal root ganglia. Spine. 1990;15(12):1248–51. 7. McCulloch JA, Young PH. Musculoskeletal and neuroanatomy of the lumbar spine. In: McCulloch JA, Young PH, editors. Essentials of spinal microsurgery. Philadelphia, PA: Lippincott-Raven; 1998. p. 249–92. 8. Suh SW, Shingade VU, Lee SH, Bae JH, Park CE, Song JY. Origin of lumbar spinal roots and their relationship to intervertebral discs: a cadaver and radiological study. J Bone Joint Surg Br. 2005;87(4):518–22.

G. Choi 9. Ruetten S, Komp M, Godolias G.  A new full-­ endoscopic technique for the interlaminar operation of lumbar disc herniations using 6-mm endoscopes: prospective 2-year results of 331 patients. Minim Invasive Neurosurg. 2006;49(2):80–7. 10. Choi G, Prada N, Modi HN, Vasavada NB, Kim JS, Lee SH.  Percutaneous endoscopic lumbar herniectomy for high-grade down-migrated L4–L5 disc through an L5–S1 interlaminar approach: a technical note. Minim Invasive Neurosurg. 2010;53(3):147–52. 11. Kim HS, Park JY.  Comparative assessment of different percutaneous endoscopic interlaminar lumbar discectomy (PEID) techniques. Pain Physician. 2013;16(4):359–67. 12. Kim CH, Chung CK.  Endoscopic interlaminar lumbar discectomy with splitting of the ligament flavum under visual control. J Spinal Disord Tech. 2012;25(4):210–7. 13. Lee JS, Kim HS, Jang JS, Jang IT. Structural preservation percutaneous endoscopic lumbar interlaminar discectomy for L5–S1 herniated nucleus pulposus. Biomed Res Int. 2016;2016:6250247.

Full Endoscopic Decompression in Thoracolumbar Stenosis Chul Woo Lee and Hyeun Sung Kim

1 Introduction Posterior open/microscopic decompression is an established gold standard treatment for the treatment of spinal canal stenosis (SCS) in lumbar and thoracic area. However, it is associated with significant paraspinal muscle damage, atrophy, iatrogenic instability, and chronic low back pain in long-term follow-up. The posterior decompression with the fusion procedure is another surgical option to guarantee enough decompression of the spinal canal and postoperative segmental stability. However, it is also associated with several complications such as instrument failure, pseudoarthrosis, and adjacent segment disease. With technical development and evolution of endoscopic instruments, endoscopic spinal surgery has become one of the standard treatments for various lumbothoracic spinal diseases ranging from a simple contained disc to complicated cases such as highly migrated disc herniation and other pathology combined with bony degeneration to produce foraminal and canal stenosis [1– 9]. Nowadays, degenerative lumbar and thoracic stenosis in the spinal canal can be treated with

C. W. Lee St. Peter’s Hospital, Seoul, Republic of Korea H. S. Kim (*) Nanoori Hospital Gangnam, Seoul, Republic of Korea

full endoscopic surgery using various accesses and techniques and several authors have reported their successful outcomes [10–12]. Full endoscopic thoracolumbar decompression in stenosis has several advantages such as minimal paraspinal muscle damage, faster postoperative recovery and rehabilitation, and minimal low back pain in long-term follow-up [13–15]. It also minimizes the damage to the posterior ligamentous complex (supraspinous ligament, interspinous ligament, and facet capsule), which acts as the posterior tension band to maintain spinal integrity, and has an advantage to preserve facet joints and avoid iatrogenic instability. In this chapter, the authors will describe indications, operative steps in detail, and surgical pitfalls and complications of full endoscopic decompression in thoracolumbar stenosis.

2 Indications 1. Spinal central canal and lateral recess stenosis –– Combined central and paracentral disc herniation –– Facet hypertrophy –– Ligament flavum (LF) hypertrophy 2. Other pathologies –– Facet joint cyst –– Ligament flavum cyst –– Ossification of ligament flavum (OLF)

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_7

49

50

3 Contraindications • Gross segmental instability evident on dynamic radiographs (>4  mm of translation or >10° angular opening) • Grade 2 or more spondylolisthesis according to Meyerding’s criteria • Severe degenerative scoliosis • Infection • Malignancy

4 Surgical Technique 4.1 Preoperative Planning 4.1.1 Plain Radiograph Plain radiographs including AP, lateral, oblique, and dynamic view of lumbar spine are routinely evaluated for the curvature of the spine (presence of degenerative scoliosis). Dynamic view is assessed for segmental instability. For surgical planning, AP view is evaluated for the extent of interlaminar window, which is reduced in most cases of spinal canal stenosis. Width of cranial, caudal laminae, and isthmus are evaluated for safe bony decompression without the excessive violation of stability-related normal structures. 4.1.2 Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) Scan The ligamentum flavum’s sublaminar and subarticular extent along with thickness are evaluated by MRI. The size, shape, and orientation of facet joints (Facet tropism) are investigated by axial CT. It gives an idea about the safe range of the medial facet resection without causing iatrogenic instability. Three-dimensional reconstructed CT scan images give an exact three-dimensional view of the interlaminar window narrowed by deviated spinous processes and hypertrophied bony spurs. Cross section area of canal and dura is measured preoperatively for the severity of stenosis and postoperatively for the adequacy of the decompression. Accompanied calcified disc and disc protrusion should also be checked as such combined pathologies need more wide

C. W. Lee and H. S. Kim

bony decompression for safe adhesiolysis and retraction of the neural structures during the operation.

4.2 Anesthesia and Position The procedure is performed under epidural anesthesia with sedation or general anesthesia for ease of patient positioning and immobilization. Local anesthesia is not preferred as interlaminar approach is accompanied by neural retraction which can evoke significant pain during the procedure. A patient is placed in a prone position on a radiolucent table with Wilson’s frame. It obliterates the lumbar lordosis and widens the interlaminar window for the safe passage of working cannula with minimal bony resection. A single dose of antibiotics is administered in the preoperative period. The entire procedure is performed under constant saline irrigation. The irrigation channel is connected with a water pump (30–40  mmHg) or a saline bag with a pole (2 m high from the operation room floor). The use of a water pump is preferred with pressure set at 30–40 mmHg. Irrigation fluid pressure should be adjusted according to the clarity of surgical fluid.

4.3 Special Surgical Instruments (Fig. 1) • Guidewire • Obturator, serial dilators, and working cannula 13.7 mm with a bevel tip • Endoscope with 15° viewing angle, outer diameter (OD) 10 mm, working channel diameter of 6 mm, and working length 125 mm: for central decompression • Endoscope with 30° viewing angle, OD 6.5  mm, working channel diameter 3.7  mm, and working length 208  mm (used in ­traditional transforaminal approach): for discectomy or contralateral foraminotomy by “Channel Switching technique” [9] • High-speed endoscopic drill with 3.5 mm diamond tip

Full Endoscopic Decompression in Thoracolumbar Stenosis

51

Fig. 1  Instruments for endoscopic posterior thoracolumbar canal decompression

• • • • •

Radiofrequency ablator with probe Endoscopic Kerrison’s rongeurs Endoscopic disc forceps Endoscopic bone cutter Endoscopic blunt bent tip probe: for releasing the ligamentum flavum from bones and others

4.4 Surgical Steps 4.4.1 Skin Incision In most cases, longitudinal incision of 1  cm in size is taken over the target point located just lateral from the spinous process on the ipsilateral side at the desired level. However, in the case of contralateral approach for contralateral foraminal decompression, the skin incision should be more laterally located at the ipsilateral medial pedicular line (1–1.5 cm lateral from midline) in order to acquire a more flat approach angle for a more easy contralateral foraminal access (Fig. 2). 4.4.2 Working Cannula Docking and Insertion of Endoscope The operative side is decided on the basis of clinical symptoms and preoperative planning. Successful decompression of the spinal canal and bilateral lateral recess could be achieved only by unilateral approach without much difficulty regardless of the approach side. Ipsilateral approach from the side where the pathology is located is preferred because the pathology and related anatomical structures

Fig. 2  Skin incision. Red colored line: skin incision for usual ipsilateral approach. Brown colored line: skin incision for contralateral approach

could be recognized early and manipulated easily. However, in the case of upper lumbar pathology and deviated spinous process, contralateral approach could be a useful alternative because of minimal facet violation and easy manipulation of the working cannula with a better operative view.

C. W. Lee and H. S. Kim

52

4.4.3 Anatomical Points In endoscopic spine surgery (ESS), the endoscopic image is different from the field of view seen under a microscope or the naked eye, so understanding the anatomical landmarks is very important for sequential endoscopic procedures. In the posterior approach, there are three anatomical points created by the ligamentum flavum and bone intersections, which serve as landmarks to facilitate the endoscope procedure. There are three target points which can be approached under fluoroscopy guidance in AP (Fig. 3). Serial dilators, obturator, and working cannula are inserted in the respective order through the space between the multifidus muscles adjacent to the spinous process, and, finally, endoscope is introduced along the working cannula. Bevel tip is docked over the lateral bony structures with a working cannula facing medially towards the ligamentum flavum in order to avoid neural injury. 4.4.4 Bony Decompression Soft tissue dissection and hemostasis are carried out with the radiofrequency ablator. Soft tissue and superficial layer of the ligamentum flavum a

b

c

d

Fig. 3  Three anatomical landmarks; Green circle (point A): Junction of medial border of ipsilateral facet and caudal lamina (initial landmark of sublaminar approach), Red circle (point B): Spino-laminar junction of cranial vertebra (initial landmark of cranial outside in (over the top) approach), Blue circle (point C): Spino-laminar junction

were removed with endoscopic forceps. Bone drilling started at the medial border of the ipsilateral facet joint (point A) from the caudal to the cranial direction and from deeper to the superficial plane up to the spino-laminar junction of the cranial vertebra (point B) (Fig. 4a) and the caudal vertebra (point C) until we observe the free margins within the deep layer of the ligamentum flavum (Fig. 4b). If required, the base of the spinous process along with the under surface of the contralateral lamina and the lateral recess is decompressed (contralateral approach) (Fig.  4c, d). Hence during endoscopic thoraco lumbar decompression (ETLD), it requires significant bone drilling of the cranial lamina compared to the caudal lamina. The interlaminar window is further narrowed with a degenerative process; hence, it requires significant bony decompression apart from soft tissue decompression, which should be carried out before the resection of LF.  It forms the basic principle of the “out and in” technique of ETLD, where the deep layer of the ligamentum flavum act as a protective barrier between the working zone and the vital structures inside the spinal canal. e

of caudal vertebra (landmark of caudal outside in (over the top) approach) in X-ray (a) AP view, (b) lateral view, (c) 3D model view, (d) intraoperative fluoroscopic view. (e) Schematic illustration of posterior two approaches (trans-laminar and sublaminar)

Full Endoscopic Decompression in Thoracolumbar Stenosis Fig. 4 Illustrative image of the sequence of bony drilling for the bilateral decompression during endoscopic lumbar canal and lateral recess decompression. (a) Drilling of the ipsilateral cranial lamina. (b) Drilling of the ipsilateral caudal lamina. (c) Drilling of the spinous process base and the contralateral sublaminar area. (d) Drilling of the medial border of the contralateral caudal lamina and facet. (e, f) Illustrative concept of the “outside in” approach

a

b

e

The operative view in endoscopic spinal surgery is very narrow and magnified during the procedure. Additionally, the unique optical angle (20–25°) of an endoscope can induce operators to have confusion in understanding the related anatomical structures. Accordingly, the knowledge of endoscopic landmarks is important for successful decompression. The principal midline landmarks for the endoscopic ipsilateral decompression are craniocaudal orientation of fibers of the ligamentum flavum, base of spinous process with interspinous ligament, and midline defect in the deep layer of LF. Laterally, the medial margin of SAP forms the lateral extent of endoscopic decompression (Fig. 5). One of the common causes of lateral recess stenosis is the pinching of the neural structures between the hypertrophied facet/facet cyst and the paracentral disc herniation. Hence, the adequate lateral recess decompression is an important step while performing ETLD.  However, excessive violation of the facet joint for complete decompression of the traversing root can cause

53

c

d

f

postoperative instability. Therefore, the operator should always be careful to preserve the facet joint. This can be achieved by rotating or tilting the endoscope towards the ipsilateral facet. Bone drilling should be followed in the medial to the lateral direction. If not, bone drilling should at least be followed in the caudal to cranial or cranial to caudal direction along the medial margin of SAP (Fig. 6).

4.4.5 Removal of the Ligament Flavum and Confirmation of the Decompressed Neural Structures All the bony decompression is performed outside the deep layer of the ligamentum flavum so that neural structures could be protected throughout the procedure. The pressure of irrigation fluid pushes the dura away from LF and develops a plane between LF and the dura. However, in certain conditions, such as the facet cyst, the ligamentum flavum cyst, and the revision surgeries, dura severely adheres to LF.  It needs careful

C. W. Lee and H. S. Kim

54 Fig. 5 (a–d) Anatomical landmarks in percutaneous endoscopic lumbar canal decompression showing the ligament flavum (asterisk), the midline (blue dotted line), the medial margin of the ipsilateral superior articular process (SAP) (red dotted curved line), and the medial margin of the contralateral SAP (white dotted curved line)

a

b

c

d

Fig. 6  Rotation and tilting maneuver of the endoscope for facet joint preservation. (a) Operative angle in lateral to medial direction. (b) Operative angle in medial to lateral direction. (c) Postoperative axial MRI image showing violated facet joint by bone drilling in lateral to medial direction. (d) Postoperative axial MRI image showing preserved facet joint by bone drilling in medial to lateral direction. Blue triangle: endoscopic field of view, Red dotted line: endoscopic optical angle for the exploration of lateral recess, and Black dotted line: operative surgical angle for drilling of bony structure

a

b

c

d

Full Endoscopic Decompression in Thoracolumbar Stenosis

a

b

55

c

Fig. 7 (a–c) Operative illustration of endoscopic intraoperative findings showing decompressed thecal sac, ipsilateral, and contralateral traversing root (asterisk)

manipulation of neural structures away from LF. Finally, the deep layer of the ligamentum flavum is elevated from its sublaminar attachment with an endoscopic dissector and the ligamentum is resected in “en bloc” fashion with the help of Kerrison’s punch and forceps. “En bloc” resection of the ligamentum flavum avoids the possibility of incomplete decompression. The switch to a smaller endoscope with OD OF 6.5  mm is preferred to perform the ventral decompression or contralateral decompression with minimal neural retraction [9]. The case in which the main pathology is central canal stenosis by hypertrophy of the ligament flavum may not need contralateral decompressive bony work. Detachment of LF in the contralateral sublamina region and its removal may suffice. However, in the cases of pure or combined bony stenosis in the contralateral region, sufficient bony decompression should always be preceded before the removal of soft tissue like LF and root exposure. Hemostasis is achieved with the help of a radiofrequency ablator. Finally, adequacy of decompression is checked by observing the free lateral recess, free floating dural sac, and the traversing nerve root in the epidural space (Fig.  7). Drain is inserted to avoid epidural hematoma collection in the postoperative period. Fascia and skin are sutured with absorbable sutures.

4.5 Postoperative Care A patient is mobilized as soon as he/she recovers from anesthesia with a lumbo-sacral corset brace. Usually, the use of braces for 2–4  weeks in the

postoperative period is recommended. There is no specific rehabilitation protocol after the surgery. The patient is allowed his/her daily routine activity if the pain is tolerable by the patient.

4.6 Consideration for Thoracic Decompression Thoracic spinal stenosis (TSS) is a reduction in the capacity of the thoracic spinal canal with associated compression of the spinal cord and/or nerve roots. It is usually caused by ossification of the ligamentum flavum (OLF), ossification of the posterior longitudinal ligament (OPLL), osteophytes, intervertebral disc herniation, and hypertrophy of the intervertebral joint. In recent years owing to advances in endoscopic technology, spinal endoscopy has been introduced as a possible treatment for intervertebral disc herniation and spinal canal stenosis in thoracic region [14, 16–19]. In thoracic region, the transforaminal approach has a distinct advantage over a posterior approach for mainly simple disc herniation in that instruments do not need to be inserted between the thecal sac and the herniation. In contrast, full endoscopic posterior thoracic approach is prioritized for patients with stenosis and ossification of the ligamentum flavum (OLF) replicating the results from open surgery. The main differences between the interlaminar approach at the thoracic and that at the lumbar levels relate to the lesser size and thickness of the lamina and more horizontal orientation of the facet joints. At the thoracolumbar junction, they assume a more oblique sagittal orientation.

C. W. Lee and H. S. Kim

56

Due to such anatomical differences from other spinal regions, the margin of decompression, in the cases of thoracic OLF and stenosis, should be determined before the operation by carefully checking MRI and CT. The amount of achieved decompression should also be confirmed by a radiograph at the end stage of the operation. The lack of a distinct landmark can be a major cause of difficulty in posterior thoracic decompression. So, many portions of the vertebral laminar and inferior articular processes need to be removed until the superior articular process (SAP) of the inferior vertebrae below the lamina of the superior vertebrae is revealed in order to identify the lesion, especially OLF. OLF confined to LF other than the fused type can be identified by partial resection of the inferior articular process by first identifying the medial boundary of SAP of the inferior vertebrae and extending the laminotomy in the upper direction. The fragility of the neural structures due to little space around the spinal cord and the limited medullary vascularization is another consideration point in endoscopic thoracic spinal surgery. The ligamentum flavum should be maintained intact until the bony decompression has been finished as it is used as a protection of the dura and the operator should be careful not to make an uncontrolled anteroposterior movement and manipulation of the dura with potential tear. The thickness of the flaval ligament increases stepwise from the upper to the lower spine and the architecture limits interlaminar endoscopic techniques for posterior and lateral pathologies. Interlaminar surgery is mainly limited to patients with stenosis and ossification of the ligamentum flavum replicating the results from open surgery. Anterior pathologies of the lateral recess may be addressed by interlaminar endoscopy, but similar to open techniques, a medial pedicle resection is necessary to create enough space to avoid manipulation of the central cord. Considering that the fused, tuberous, and beak type of OLF adhere to the dura mater or fuses with ossifications, total laminectomy and concomitant fusion are recommended because of the technical difficulties and the high risk of dural tear and its reconstruction. For the same

reason, OLF with comma and tram track signs would not be recommended as an indication of endoscopic thoracic surgery. There is more concern about the potential risk of neurological complications due to locally isolated irrigation fluid in the epidural space, which could increase the intracranial pressure (IICP) in endoscopic thoracic surgery compared to the lumbar region. Operators should always make an effort to reduce the operation time and monitor good patency of input/output of irrigation channels during the operation. In endoscopic thoracic decompression surgery, if dura tear occurs at an early stage of the operation, even though the size of the dura tear is small, conversion to open surgery is recommended in order to avoid the negative consequences of IICP.

5 Complications 5.1 Incomplete Decompression and Excessive Facet Violation Common mistakes which beginners make in the early learning curve of endoscopic thoracolumbar decompression are incomplete decompression and facet violation. To avoid incomplete decompression, the operator should determine the extent of the decompression by preoperative radiologic evaluation before the operation. Usually, anatomical landmarks for ideal bony decompression are the upper and lower margin of LF (craniocaudal) and the medial margin of SAP (lateral). More cranial resection of the upper lamina is needed in the cases of listhesis and bulging central disc. In cases of severe facet hypertrophy and engulfed lateral recess, medial facet joint resection should be extended more laterally for adequate decompression of the traversing root. Excessive facet violation is mostly caused by misunderstanding of the distorted angle of the endoscopic view. To avoid facet over-resection in endoscopic thoracolumbar decompression, the operator should fully understand and know the difference between the optical angle and the real operative angle of the

Full Endoscopic Decompression in Thoracolumbar Stenosis

57

spinal endoscope which is used in ESS. Use of optical angle, rotatability, and tilting of the endoscope is helpful to prevent facet over-resection (Fig. 6).

Postoperative drain is recommended after the operation to prevent postoperative hematoma.

5.2 Intraoperative Bleeding

Dura tear is a serious complication in ETLD. It can lead to adverse consequences such as intraoperative increased intracranial pressure, postoperative rootlet expulsion, persistent CSF leakage from the operative wound, and pseudomeningocele, which needs secondary revision surgery. There exists a higher chance of dural tear in ESS compared with conventional spinal surgery. The operator should be more careful with cases that have a higher risk of dura tear, such as aged patients, severe stenosis with adhesion, and revision surgery. To prevent intraoperative dural tears, the surgeon should be aware of the blind spots where the endoscope does not provide operative view when endoscopic instruments are used around the neural structures. Variable endoscopic operative angles and views can be acquired by tilting and rotating the endoscope. Such an endoscope maneuver could help the operator to identify the hidden areas beyond the limitation of static endoscopic view. Double checking by such an optimized endoscopic view, which may show the intersurface between the dura and the adjacent structures, should be done whenever the operator uses endoscopic drills or punches near the dura. Maintaining a clear operative field is important in order to lower the risk of dura tear because dura tear often occurs accidentally under obscured endoscopic view from intraoperative bleeding during ligament flavum resection. Despite careful management of the dura, if the dura tear occurs at an early stage or the size of the dura tear is large, conversion to open surgery is needed for dura suture. However, in the case of a small dura tear at the late stage of the surgery, the operator could continue the operation after sealing procedure. Most of the small nick of the dura tear can be treated by sealing with Gelfoam (Pfizer Inc., New York, USA) and TachoSil sealant patch (Baxter Healthcare Corporation, Deerfield, Illinois, USA) and postoperative absolute bed rest.

It is a prerequisite to preserve a clear operative view in order to shorten the operative time with smooth operation and perform safe surgery with less complications. Preoperative cessation of anticoagulant use should be always checked. Systolic blood pressure in the range of 100– 110  mmHg is recommended to decrease the chance of obscure operative view by minor bleeding. Adequate control of the irrigation pressure and strict hemostasis are keys to preserve the clear operative fields in endoscopic spine surgery. Beforehand bleeding control is a solution to prevent troublesome intraoperative bleeding. Areas where frequent major bleeding is encountered are around the venous plexus at the cranial portion beyond the upper margin of the ligament flavum, lateral recess area, and intramuscular artery around the lamino-facet junction. When an operator encounters a blurred operative view due to unknown origin bleeding, the operator should always first check the good patency of the irrigation pathway, such as shortage of water supply, clogging of the irrigation line, and all orifices of the instruments. Initial water pump pressure is preferred to be set at 30–40  mmHg. Temporary elevation of the irrigation fluid pressure is helpful to find the bleeding focus and cope with such troublesome intraoperative bleeding. However, the temporary elevation of the irrigation pressure should be limited to a very short time and below 50 mmHg at any time. Drilled bony margin and dissected muscles in the outside of the working cannula should also be considered as one of the unknown origins which blur the operative view. Uncontrollable intraoperative bleeding from unknown origin is rare. “Wait and see” strategy after the application of the hemostatic agent (Floseal®, Baxter Healthcare, Hayward, CA) through the cannula can be a practical countermeasure to figure out such an obstinate situation.

5.3 Incidental Durotomy

58

5.4 Injury to Neural Structures/ Transient Dysesthesia Neural complications, such as postoperative dysesthesia and motor weakness, usually result from the careless use of operative instruments in limited operative fields with narrow interlaminar and intracanal space. Another common cause is excessive manipulation of the neural structures before adequate initial decompression and adhesiolysis from perineural structures. Continuous use of radiofrequency (RF) coagulation with high power can be one of the other reasons. Prevention is the best way of managing the neural complication. Endoscopic vision should be always clear, which can be achieved by increasing the fluid pressure momentarily and strict hemostasis. Several risky situations such as combined protruded discs, especially highly migrated discs, and high canal compromised cases may need a wide range of bony resection for safety. Such a strategy of bony decompression should be also applied to cases of suspicious perineural adhesion which had a long duration of symptom, calcified disc, and revision. “Decompression first (by bony unroofing or discectomy) and manipulation second” should be a strategic principle to minimize neural injury. Initial adequate decompression, including bone work, discectomy, and

C. W. Lee and H. S. Kim

perineural adhesiolysis, should be preceded before the manipulation of the neural structures. If adequate decompression is uncertain with tense root and difficult root mobilization, additional extended lamino-facetectomy should be performed before root manipulation and discectomy. Even after adequate decompression by widening of the interlaminar window and discectomy, meticulous adhesiolysis should be obtained without retraction of the neural structures, and then manipulation of the nerve root should be done in a very careful manner with minimal and intermittent retraction in order to minimize the risk of neural injury. The operator should also always stick to the use of bipolar RF with adequate intensity (soft tissue ablation and bone bleeding control: 250  W, but around the neural structures: below 90  W) to avoid postoperative dysesthesia.

6 Illustrative Cases 6.1 Case 1. Severe Lumbar Canal Stenosis Combined with Disc Herniation (Fig. 8) A 76-year-old woman had suffered from bilateral buttock and leg pain. She was unable to

Fig. 8  Preoperative and postoperative T2 MRI images of a 76-year-old female patient with L3–4 severe spinal canal stenosis (Schiza’s grade D) treated with endoscopic lumbar canal decompression

Full Endoscopic Decompression in Thoracolumbar Stenosis

walk for 3  min despite conservative treatment for 6 months. On examination, VAS score was 8 for back pain and left-side dominant (L5 dermatome) bilateral leg pain. Preoperative MRI showed severe spinal canal stenosis combined with inferior migrated disc on L4/5 level. No slippage and instability sign was seen in dynamic X-rays. Patient underwent endoscopic laminectomy and removal of the herniated disc. During the operation, the dura was exposed after hypertrophied thick ligament flavum was detached from the dura and removed. Significant adhesion between the nerve root and surrounding structures was observed. A ruptured disc was found after meticulous adhesiolysis and careful retraction of the nerve root. Fragmentectomy with internal debulking of the disc was performed successfully. Postoperatively, the patient had complete resolution of the bilateral buttock and leg pain. Postoperative MRI showed favorable operative results with a widened spinal canal and successful removal of the disc. Minimal signal change in paraspinal muscles was observed in postoperative MRI.

59

6.2 Case 2. Multilevel Endoscopic Lumbar Canal Decompression (Fig. 9) A 67-year-old man had been treated conservatively for his low back pain and neurogenic intermittent claudication for about 2 years. However, the patient’s pain deteriorated. Lumbar MRI confirmed his intolerable pain was caused by multilevel spinal canal stenosis in L3/4, 4/5, and L5/S1. The patient underwent multilevel endoscopic spinal canal decompression. The operation was performed with 1 cm long two skin incisions, one for L3/4 and the other for L4/5/S1. During the operation, a very thin dura due to long-time compression with degenerative change was observed after partial laminectomy and ligament flavectomy. Fully decompressed thecal sac and nerve roots were confirmed. After the surgery, the patient’s low back and leg pain were dramatically improved without any neurologic deficit. The patient was able to walk well without any limitation and was discharged 2 days after the operation. The patient’s good clinical outcome has been observed for 2 years without further treatment.

Fig. 9  Preoperative and postoperative T2 MRI images of a 76-year-old male patient with multilevel spinal canal stenosis treated with endoscopic lumbar canal decompression

C. W. Lee and H. S. Kim

60

6.3 Case 3. Ossification of ligament Flavum in Lumbar Area (Fig. 10) A 52-year-old man presented with right side leg pain of 2 years duration with inability to walk over 10 min with, on examination, VAS score of 5 and 8 for back and leg pain. Routine X-ray revealed no evidence of instability and MRI and CT showed ossified ligament flavum compressing the neural structures in the spinal canal at L4/5 level. The patient underwent spinal decompression with the removal of only the right side of OLF via a uniportal endoscopic approach because the patient’s symptom was unilateral. Intraoperatively, thinning of the thick OLF by drill was needed in order to dissect OLF from the adhesed dura more easily and safely. Eggshell-­ like thinned fragments of OLF were gently detached from the dura to avoid dura tear and removed in a piecemeal manner by endoscopic punch. Decompressed thecal sac and nerve root of the ipsilateral side were observed. Postoperatively, the patient had resolution of the back and leg pain with no features of immediate

postoperative complications. Postoperative MRI and CT showed successful removal of OLF in the right side and decompressed spinal canal.

7 Summary Endoscopic lumbar decompression is a good surgical option to treat thoracolumbar stenosis with many advantages in MIS perspective. The advantages of this technique are considered in terms of less intraoperative blood loss, minimal damage to the soft tissue, and early postoperative recovery with preservation of the spinal stability in long-­ term follow-up. Although a steep learning curve exists due to technical difficulty, unfamiliar endoscopic anatomy, and unaccustomed surgical equipment, continued surgical experience will give a spinal surgeon rewarding success with endoscopic thoracolumbar decompression. Percutaneous full endoscopic thoracolumbar decompression is a safe, clinically feasible, and effective surgical technique and can be considered as a primary treatment for thoracolumbar stenosis.

Fig. 10  Preoperative and postoperative CT and T2 axial MRI images of a 52-year-old male patient whose ossified ligament flavum was treated with endoscopic removal of unilateral OLF. Decompressed thecal sac and root (asterisk) were revealed after the removal of the thinned eggshell of OLF (black arrow)

Full Endoscopic Decompression in Thoracolumbar Stenosis

References 1. Telfeian AE, Veeravagu A, Oyelese AA, Gokaslan ZL.  A brief history of endoscopic spine surgery. Neurosurg Focus. 2016;40(2):E2. https://doi. org/10.3171/2015.11.FOCUS15429. 2. Khandge AV, Sharma SB, Kim JS.  The evolution of transforaminal endoscopic spine surgery. World Neurosurg. 2020:1–14. https://doi.org/10.1016/j. wneu.2020.08.096. 3. Lee CW, Ph D, Yoon KJK-J, et  al. Foraminoplastic superior vertebral notch approach with reamers in percutaneous endoscopic lumbar discectomy: technical note and clinical outcome in limited indications of percutaneous endoscopic lumbar discectomy. J Korean Neurosurg Soc. 2016;59(2):172–81. https:// doi.org/10.3340/jkns.2016.59.2.172. 4. Kim HS, Adsul N, Kapoor A, et al. A mobile outside­in technique of transforaminal lumbar endoscopy for lumbar disc herniations. J Vis Exp. 2018;2018(138):1– 7. https://doi.org/10.3791/57999. 5. Ahn Y, Oh HK, Kim H, Lee SH, Lee HN. Percutaneous endoscopic lumbar foraminotomy: an advanced surgical technique and clinical outcomes. Neurosurgery. 2014;75(2):124–32. https://doi.org/10.1227/ NEU.0000000000000361. 6. Ruetten S, Komp M, Merk H, Godolias G.  Surgical treatment for lumbar lateral recess stenosis with the full-endoscopic interlaminar approach versus conventional microsurgical technique: a prospective, randomized, controlled study. J Neurosurg Spine. 2009;10(5):476–85. https://doi. org/10.3171/2008.7.17634. 7. Choi G, Lee S-H, Lokhande P, et  al. Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique using rigid working channel endoscope. Spine (Phila Pa 1976). 2008;33(15):E508–15. https://doi. org/10.1097/BRS.0b013e31817bfa1a. 8. Lee CW, Yoon KJ. Technical considerations in endoscopic lumbar decompression. World Neurosurg. 2020;145:663–9. https://doi.org/10.1016/j. wneu.2020.07.065. 9. Kim HS, Patel R, Paudel B, et  al. Early outcomes of endoscopic contralateral foraminal and lateral recess decompression via an interlaminar approach in patients with unilateral radiculopathy from unilateral foraminal stenosis. World Neurosurg. 2017;108:763– 73. https://doi.org/10.1016/j.wneu.2017.09.018. 10. Lee CW, Yoon KJ, Jun JH. Percutaneous endoscopic laminotomy with flavectomy by uniportal, unilateral

61

approach for the lumbar canal or lateral recess stenosis. World Neurosurg. 2018; https://doi.org/10.1016/j. wneu.2018.01.195. 11. Lee C-H, Choi M, Ryu DS, et  al. Efficacy and safety of full-endoscopic decompression via interlaminar approach for central or lateral recess spinal stenosis of the lumbar spine. Spine (Phila Pa 1976). 2018;43(24):1. https://doi.org/10.1097/ BRS.0000000000002708. 12. McGrath LB, White-Dzuro GA, Hofstetter CP.  Comparison of clinical outcomes following minimally invasive or lumbar endoscopic unilateral laminotomy for bilateral decompression. J Neurosurg Spine. 2019;30(4):491–9. https://doi.org/10.3171/201 8.9.spine18689. 13. Lee CW, Yoon KJ, Ha SS.  Comparative analysis between three different lumbar decompression techniques (microscopic, tubular, and endoscopic) in lumbar canal and lateral recess stenosis: preliminary report. Biomed Res Int. 2019;2019:5–12. 14. Yang FK, Li PF, Dou CT, Yu RB, Chen B. Comparison of percutaneous endoscopic thoracic decompression and posterior thoracic laminectomy for treating thoracic ossification of the ligamentum flavum: a retrospective study. BMC Surg. 2022;22(1):1–7. https:// doi.org/10.1186/s12893-­022-­01532-­z. 15. Kim HS, Paudel B, Jang JS, et al. Percutaneous full endoscopic bilateral lumbar decompression of spinal stenosis through uniportal-contralateral approach: techniques and preliminary results. World Neurosurg. 2017;103:201–9. https://doi.org/10.1016/j. wneu.2017.03.130. 16. Gibson RDS, Wagner R, Gibson JNA. Full endoscopic surgery for thoracic pathology: an assessment of supportive evidence. EFORT Open Rev. 2021;6(1):51– 60. https://doi.org/10.1302/2058-­5241.6.200080. 17. Wu W, Diao W, Yang S, Guo Y, Yan M, Luo F. The effect of using visual trepan to treat single-segment ossification of ligamentum flavum under the endoscope. World Neurosurg. 2019;131:e550–6. https:// doi.org/10.1016/j.wneu.2019.07.223. 18. Kang MS, Chung HJ, You KH, Park HJ. How i do it: biportal endoscopic thoracic decompression for ossification of the ligamentum flavum. Acta Neurochir (Wien). 2022;164(1):43–7. https://doi.org/10.1007/ s00701-­021-­05031-­7. 19. Zheng C, Liao Z, Chen HZ. Percutaneous endoscopic posterior decompression for therapy of spinal cord compression due to ossification of the ligamentum flavum: a long-term follow-up. World Neurosurg. 2021;156:e249–53. https://doi.org/10.1016/j. wneu.2021.09.044.

Transforaminal Endoscopic Lumbar Lateral Recess Decompression Sang-Ha Shin

1 Introduction Spinal stenosis is the result of degenerative changes in the bone, disc, capsule, and ligament [1, 2]. Surgical treatment including decompression and fusion surgery may be considered when there is no response to conventional treatment. Recently, stability-preserving decompression technique has been attracting attention in case of radiating pain-dominant spinal stenosis without severe segmental instability [3–6]. Transforaminal endoscopic treatment has been reported to be an effective treatment option in patients with lumbar disc herniation because of the advantages such as progression under local anesthesia, rapid recovery, and minimization of postoperative spinal instability without excessive bone and facet joint resection [7, 8]. Endoscopic decompression is becoming popular in the treatment of lumbar disc disease due to increased patient demand and development of endoscopic devices. However, it is rarely performed for spinal stenosis because of the limitation of endoscopic working mobility due to the

exiting nerve root and foraminous bony structure. In this chapter, we describe the transforaminal endoscopic decompression technique for lateral recess stenosis.

2 Indications Patients with profound large disc herniation, migrated disc herniation, or bilateral leg pain are excluded. Transforaminal approach is difficult to perform in patients with high iliac crest, narrow foramen, and large facet joint at L5/S1 level. These patients are also excluded. In addition, patients with segmental instability or spondylolisthesis, profound adjacent segment spine disease, revision surgery, or profound motor weakness is excluded. Segmental instability was determined when sagittal plane displacement is more than 4 mm, or sagittal plane angulation is more than 15° in L3–4, more than 20° in L4–5, and more than 25° in L5–S1 in the lateral flexion-­ extension X-ray.

Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/978-­981-­19-­9849-­2_8. S.-H. Shin (*) Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_8

63

S.-H. Shin

64

a

b

c

Fig. 1 Schematic illustrations of endoscopic lateral recess decompression. (a) Extreme lateral transforaminal approach with foraminoplasty. (b) Partial upper pediculectomy of the lower pedicle following vertical foraminal

3 Surgical Technique 3.1 Preoperative Planning The access angle approaches approximately 15° in the horizontal plane of the axial image (Fig.  1a). As in the conventional transforaminal approach, approaching the angle of 30° can cause facet joint destruction, and it is difficult to obtain visibility when removing the dorsal ligament flavum. The distance from the midline to the skin entry point was calculated via evaluation of magnetic resonance imaging (MRI) or computed tomography (CT) axial images. This distance is about 13–16 cm, which is farther than the distance of a typical transforaminal approach. The extreme lateral approach may impair the paravertebral tissue or abdominal contents because the approach angle is shallower than the conventional approach. To prevent such complications, it is most important to identify the appropriate trajectory in the preoperative MRI axial image. It is also safer to approach the lateral projection guide in the fluoroscopic image when inserting the introducer needle, and it is important to regularly check the needle position. The craniocaudal skin entry point was determined parallel to the disc space because

d

widening. (c) Removal of the ligamentum flavum in the lateral portion of the spinal canal. (d) Removal of the ligamentum flavum in the dorsal portion of the spinal canal

it provides the best working mobility vertically during lateral recess decompression.

3.2 Surgical Steps The surgical procedure included four steps: extreme lateral transforaminal approach with foraminoplasty, partial upper pediculectomy of the lower pedicle following vertical foraminal widening, removal of the lateral ligamentum flavum covering the traversing nerve root, removal of the ligamentum flavum in the lateral portion of the spinal canal, and removal of ligamentum flavum in the dorsal portion of the spinal canal (see Video 1).

3.2.1 Extreme Lateral Transforaminal Approach with Foraminoplasty The procedure was performed under fluoroscopic guidance after local anesthesia in a slightly flexion-­prone position on the radiolucent table in all patients. After administration of local anesthetics, an 18-gauge introducer needle was inserted at the skin entry point. Transforaminal block was performed to reduce pain during the procedure after accessing the foramen. The contrast was then injected to confirm the lateral mar-

Transforaminal Endoscopic Lumbar Lateral Recess Decompression

gin of the dural sac and the location of the exiting nerve root. The needle was pulled back and landed on the lateral edge of the superior articular process. The inferior part of the superior articular process was undercut to the medial pedicular line on the fluoroscopic anteroposterior image using a serial bone reamer.

3.2.2 Partial Upper Pediculectomy of the Lower Pedicle Following Vertical Foraminal Widening After the insertion of the working cannula and endoscope along the reamed superior articular process, the opening of the bevel was directed to the cranial direction to secure the working space. Next, a vertical foraminal widening was performed by drilling the superior portion of the superior articular process using an endoscopic drill (Fig. 1b). With the bevel opening facing the caudal end, the inferior portion of the superior articular process and the upper portion of the pedicle of the lower vertebra were removed. The partial upper pediculotomy of the lower vertebra allows the complete decompression of the medial and lateral portions of the traversing nerve root in the subarticular zone of the pedicle level. Foraminal widening should be performed carefully not to exceed the height of the reamed superior articular process at the first approach to prevent facet joint damage. 3.2.3 Removal of the Ligamentum Flavum in the Lateral Portion of the Spinal Canal After foraminal widening and upper pediculectomy, vertical control of the working cannula is possible. Removal of the remnant osseous fragment using a diamond drill and side-firing holmium yttrium-aluminum-garnet (HO:YAG) laser (Lumenis Inc., NY) in the subarticular zone exposes the ligamentum flavum and epidural fat tissue (Fig. 1c). Using a dissection probe, the neural element and surrounding tissue were separated by meticulous dissection, and punch and forceps were used to remove the ligamentum flavum covering the

65

lateral side of the traversing nerve root. During dissection, epidural bleeding may blur the field of view. Therefore, it is necessary to pay attention to hemostasis and sufficient pain control because it can appeal to the pain when the nerve is touched.

3.2.4 Removal of the Ligamentum Flavum in the Dorsal Portion of the Spinal Canal To decompress the dorsal portion of the traversing nerve root, the working cannula was floated in the epidural space using the levering technique to ensure visibility of the dorsal portion (Fig.  1d). After dissection using a probe between the nerve root and the dorsal ligamentum flavum, the side-­ firing laser tip was placed on the nerve root and the dorsal ligamentum flavum was removed using a laser. The endpoint of dorsal decompression was sagittal inspection from the medial margin of the lower pedicle to the axillary portion of the traversing nerve root and axillary inspecting from the origin of the exiting nerve root around the upper pedicle to the mid-pedicular level of the lower pedicle. After decompression, hemostasis was checked, and the endoscope was removed. The skin wound was closed with a subcutaneous suture and applied to the wound closure strip. 3.2.5 Ventral Decompression (If Necessary) Dorso-ventral decompression is required in lateral recess stenosis, where ventral neural compression due to osteophytic spur or extruded disc is accompanied by dorsal neural compression. In this case, after dorsal decompression, ventral lesion was exposed by dissecting between the ventricular dura of disc level and posterior longitudinal ligament. Because of the nature of the endoscopic access approaching the lateral approach, traction of the nerve during ventral dissection was minimized. In the case of an extruded disc, it is possible to selectively remove the disc that is compressing the nerve after creating a small annular hole. When the nerve was compressed by the posterior osteo-

S.-H. Shin

66

a

b

c

Fig. 2  Illustrative case of lateral recess stenosis causing dorsal neural compression. (a) Preoperative computed tomography (CT) images showing lateral recess stenosis due to ligamentum flavum and facet joint hypertrophy. (b) Postoperative CT images showing complete decompression of the left lateral recess. (c) The bone setting image on the CT showing the preservation of the left facet joint

phytic spur, complete decompression was possible by laser or drill after retraction of the nerve to the medial side using the blocked side of the beveled working cannula.

4 Case illustration 4.1 Case 1 A 50-year-old female patient presented with left leg pain. Preoperative Computed Tomography (CT) images revealed lateral recess stenosis caused by ligamentum flavum and facet joint hypertrophy (Fig. 2a). After endoscopic foraminotomy, the patient’s symptom improved and postoperative CT images showed complete

decompression of the left lateral recess. The bone-setting image on the CT scan demonstrated the preservation of the left facet joint (Fig. 2b).

4.2 Case 2 A 63-year-old female patient presented with left leg pain. Preoperative magnetic MR and CT images showed a lateral recess stenosis where ventral neural compression caused by osteophytic spur or extruded disc is accompanied by dorsal neural compression (Fig.  3a). After endoscopic foraminotomy, the patient’s symptom was relieved and postoperative MR and CT images showed complete decompression of the left lateral recess with preservation of the facet joint (Fig. 3b).

Transforaminal Endoscopic Lumbar Lateral Recess Decompression

67

a

b

Fig. 3  Illustrative case of lateral recess stenosis causing dorsoventral neural compression. (a) Preoperative magnetic resonance (MR) and CT images showing lateral recess stenosis where ventral neural compression due to osteophytic spur or extruded disc is accompanied by dorsal neural compression. (b) Postoperative MR and CT images showing complete decompression of the left lateral recess with preservation of the facet joint

5 Complication Avoidance

bilateral lower limb symptoms. Third, this technique can be performed by a spine surgeon skilled Open laminectomy has been performed as a stan- in endoscopic treatment. dard surgical treatment option for decompression Transforaminal endoscopic decompression of the lateral recess stenosis [9]. In our clinical of patients with spinal stenosis has the followcase series, patients with endoscopic decompres- ing characteristics when compared with convension of spinal stenosis improved back and leg tional open surgery. First, it can be performed pain and did not show major complications such under local anesthesia; the operation duration as dural tear or infection [10]. is short with less blood loss. These advantages The endoscopic transforaminal decompres- may be good treatment options for the elderly sion technique has the following limitations. or medically compromised patients who have First, central zone decompression is difficult. difficulty with general anesthesia. Second, facet After the lateral approach, the thecal sac is dome-­ joint damage can be minimized by approachshaped. After decompression of the subarticular ing through the extreme lateral approach, and zone, central zone decompression is difficult there is no posterior ligamentous structure and since the surgical field is limited because the muscle damage. This may reduce postoperative nerve mounts gradually toward the central zone. segmental instability or spondylolisthesis. Third, Second, it is difficult to apply to patients with by approaching the transforaminal route, decom-

S.-H. Shin

68

a

b

Fig. 4  Illustrative case of disc herniation accompanying lateral recess stenosis. (a) Preoperative MR images showing downward migrated disc herniation with lateral recess stenosis. (b) Postoperative MR images showing decompression of the left lateral recess with removal of the herniated disc compressing the neural structures

pression can be performed simultaneously with lateral recess stenosis and foraminal lesions. In the lateral recess stenosis with foraminal compressive lesion, the posterior decompression requires extensive facet joint resection on the unilateral side. This technological approach has the advantage of minimizing iatrogenic facet joint destruction and simultaneous decompression of foramen lesions. Fourth, decompression can be performed simultaneously with lateral recess stenosis accompanying disc herniation with this technique. Even with highly migrated

disc herniation, the control of the working cannula is free because of vertical foraminal widening; hence, the accompanying herniated disc can be easily removed (Fig.  4). Some authors reported that endoscopic treatment in patients with disc herniation with lateral recess stenosis has poor surgical outcomes [7, 11]. However, the new technique described in this study may provide good results if the decompression of the herniated disc is performed simultaneously after adequate decompression of the lateral recess stenosis.

Transforaminal Endoscopic Lumbar Lateral Recess Decompression

This endoscopic technique can be applied to various spinal diseases. Furthermore, it can be used as a minimally invasive treatment option for dorsal compressive pathologies such as facet synovial cyst, ligamentum flavum cyst, epidural hematoma, or abscess. In addition, we believe that this technique can be developed to provide both decompression and fusion at the same time by combining with endoscopic lumbar interbody fusion.

6 Summary Transforaminal endoscopic decompression under local anesthesia could be an effective treatment method for the selected group of patients with spinal stenosis. It can be performed under local anesthesia; the operation time is short with less blood loss. Furthermore, facet joint damage can be minimized through the extreme lateral approach. This technique can be used as a minimally invasive treatment option for dorsal compressive pathologies such as facet synovial cyst, ligamentum flavum cyst, epidural hematoma, or abscess.

References 1. Weinstein JN, Lurie JD, Tosteson TD, Hanscom B, Tosteson AN, Blood EA, et al. Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis. N Engl J Med. 2007;356(22):2257–70. 2. Weinstein JN, Lurie JD, Tosteson TD, Zhao W, Blood EA, Tosteson AN, et al. Surgical compared with nonoperative treatment for lumbar d­egenerative spon-

69

dylolisthesis. Four-year results in the Spine Patient Outcomes Research Trial (SPORT) randomized and observational cohorts. J Bone Joint Surg Am. 2009;91(6):1295–304. 3. Kleeman TJ, Hiscoe AC, Berg EE.  Patient outcomes after minimally destabilizing lumbar stenosis decompression: the “Port-Hole” technique. Spine. 2000;25(7):865–70. 4. Poletti CE.  Central lumbar stenosis caused by ligamentum flavum: unilateral laminotomy for bilateral ligamentectomy: preliminary report of two cases. Neurosurgery. 1995;37(2):343–7. 5. Schöller K, Alimi M, Cong GT, Christos P, Härtl R.  Lumbar spinal stenosis associated with degenerative lumbar spondylolisthesis: a systematic review and meta-analysis of secondary fusion rates following open vs minimally invasive decompression. Neurosurgery. 2017;80(3):355–67. 6. Spetzger U, Bertalanffy H, Naujokat C, von Keyserlingk DG, Gilsbach JM.  Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: anatomical and surgical considerations. Acta Neurochir (Wien). 1997;139(5):392–6. 7. Ahn Y, Lee SH, Park WM, Lee HY, Shin SW, Kang HY.  Percutaneous endoscopic lumbar discectomy for recurrent disc herniation: surgical technique, outcome, and prognostic factors of 43 consecutive cases. Spine. 2004;29:E326–32. 8. Shin SH, Hwang BW, Keum HJ, Lee SJ, Park SJ, Lee SH. Epidural steroids after a percutaneous endoscopic lumbar discectomy. Spine. 2015;40(15):E859–65. 9. Watters WC 3rd, Bono CM, Gilbert TJ, Kreiner DS, Mazanec DJ, Shaffer WO, et  al. An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spondylolisthesis. Spine J. 2009;9(7):609–14. 10. Shin SH, Bae JS, Lee SH, Keum HJ, Kim HJ, Jang WS.  Transforaminal endoscopic decompression for lumbar spinal stenosis: a novel surgical technique and clinical outcomes. World Neurosurg. 2018;114:E873–82. 11. Choi KC, Lee JH, Kim JS.  Unsuccessful percutaneous endoscopic lumbar discectomy: a single-­ center experience of 10228 cases. Neurosurgery. 2015;76:372–81.

Transforaminal Endoscopic Lumbar Foraminotomy/ Foraminoplasty Jung-Hoon Kim, Jin-Sung Kim, Young-Jin Kim, and Kyung-Sik Ryu

1 Main Script Lumbar spinal stenosis (LSS) is a disease that refers to a condition in which the spinal canal is narrowed and causes compression of the nerve root and thecal sac. LSS is usually encountered in patients aged 60  years or older and is the most common cause of back pain. The condition of this disease was first described by Antonie Patel in 1803. In the 1950s, Verbiest first named the term spinal stenosis, and also described the factors associated with this disease. As a pathological part of LSS, the progression of degenerative changes usually starts in the disc, but first, due to the decrease of nutrients inside the disc, cell rupture or matrix degradation occurs. This phenomenon causes the weakening of the annulus fibrosus of the disc due to the conduction of physical pressure, swelling or bulging that invades the spinal canal, the formation of osteophyte, and degeneration of the facet joint. As such, further erosion occurs in the lateral recess, corresponding to the pedicle and disc height, due to Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/978-­981-­19-­9849-­2_9.

J.-H. Kim · J.-S. Kim (*) · Y.-J. Kim · K.-S. Ryu Department of Neurosurgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea

degenerative changes in the facet joint. In addition, the yellow ligament thickly surrounds the lateral and central regions and also reduces the size of the intervertebral foramen due to a sagittal plane disruption as the disc space narrows. Anatomically, LSS is classified into lateral recess or subarticular, foraminal and extraforaminal stenosis, including the central, depending on the area being compressed. Details of IESS (Interlaminar endoscopic spine surgery) used as a treatment for central and paracentral lesions have been reported by Chen et  al. [1]. Foraminal stenosis (FS) is caused by a decrease in the intervertebral disc space, the formation of osteophytes of vertebral endplate and facet joint, and herniation of the disc. Extraforaminal stenosis is caused by compression of the exiting root in patients with degenerative scoliosis, isthmic spondylolisthesis, or extreme extraforaminal disc herniation. This is the space between the ala of the sacrum and the transverse process and disc of the fifth lumbar vertebra, and most of them occur in the fifth lumbar vertebrae and the first sacrum level. According to the pathophysiological mechanism of FS, when the exiting nerve root of the relevant segment is pressed, various neurological symptoms including radiating pain appear. Patients with FS undergo various procedures including selective nerve root block due to such radicular pain, and if the severity gets worse, surgical treatment is considered. However, in the case of classic open surgery, physical damage to the back muscles around the

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_9

71

72

spine [2–5], which inevitably occurs during the surgical process, has the disadvantage of causing pain at the surgical site, spinal instability, and imbalance [6–9]. In the case of minimally invasive surgery such as endoscopic surgery, it has been confirmed that postoperative muscle damage can be reduced depending on the wound size and approach direction and method [10]. As a treatment for FS using this endoscopic approach, TELF/TELD is a technique that enables the selective removal of neural compromising structure that causes the patient’s symptoms within the range that guarantees the stability of the facet joint without damaging the muscles around the spine. Through this process, it can be said that the endoscopic treatment for FS is particularly important in that it can reduce the patient’s pain and at the same time minimize the occurrence of complications such as spinal instability that may occur later. While the first endoscopic foraminotomy was reported in the early 2000s, technical and technological advances allowed a safer and more efficient procedure, adopting an “outside-in” approach to the stenotic foramen [11].

2 Technical Description When considering endoscopic foraminotomy, the site of stenosis can come in various forms and the technique requires decompression in two main directions. 1. Basic steps—step 1/2 (a) Standard superior articular process (SAP)-based foraminal decompression The transforaminal resection of SAP tip serves as baseline for endoscopic foraminoplasty. As a consequence, it is considered as the first and indispensable surgical module. Endoscopic transforaminal SAP resection follows the technique described by Ahn et al. [12]. Puncture site is calculated using preoperative MRI.  Needle is advanced until the tip contacts the transition between pedicle and SAP. An 8 mm skin incision is made,

J.-H. Kim et al.

and guidewire, blunt dilator, and beveled working sheath are placed sequentially. The opening of the beveled working sheath must be “floating free” into the foramen, in gentle contact with the SAP surface. The endoscope is placed through the working sheath and then the resection of the tip of the SAP is carried out under endoscopic visualization using an endoscopic high-speed drill. Redundant ligamentum flavum must be removed as well to complete the decompression. (b) Transforaminal lateral recess decompression: levering maneuver Lateral recess decompression can be accomplished both through interlaminar access or transforaminal access [13]. The latter requires a “levering maneuver” that consists in tilting the tip of the endoscope anterior and medial to advance through the previously enlarged foramen into the limits of the lateral recess. An extended resection of the SAP is carried out, and the loosened ligamentum flavum is removed. The resection ends when the traversing nerve root is freed from the axilla of the exiting nerve root (cranial limit) to the inferior pedicle (caudal limit). 2. Basic steps—step 3/4 (c) Cranial to caudal direction: 3C technique As the name suggests, the most important part of TELF is to completely decompress the intervertebral foramen. For this, not only the simple central decompression but also the cranial to caudal decompression are required, which the author will call the 3C technique (or 3 points decompression). In this technique, decompression is performed from the lower pedicle of the upper vertebral body forming the intervertebral foramen to the upper boundary of the pedicle of the lower vertebral body by dividing the intervertebral foramen into the central, caudal, and cranial portion as shown in Fig. 1. Then, during surgery, C-arm fluoroscopy can be used to check whether complete decompression has been achieved.

Transforaminal Endoscopic Lumbar Foraminotomy/Foraminoplasty

73

Fig. 1  Illustration explaining the 3C technique

(d) Dorsal to ventral direction: osteophyte resection and disc fragmentectomy Osteophytes arising from the superior or inferior vertebrae’s endplate can be responsible for ventral foraminal stenosis and contribute to exiting nerve root compression. To safely remove these formations, it is preferable to rotate the working sheath until the bevel is covering and protecting the exiting nerve root. Then, proceed to “cavitate” the osteophyte with a diamond burr, keeping intact the bone layer that is in contact with the nerve root. Finally, with a blunt dissector, gently fracture the remaining thin layer of osteophyte away from the nerve root, as described by Lee et al. [14]. Another structure that can cause ventral foraminal stenosis and exiting nerve root compression is a herniated intervertebral disc. The disc fragment can be removed according to the outside-in technique described by Hoogland and Schubert [15], simplified by the previ-

ous foraminotomy. However, when dealing with a voluminous disc herniation, an early access to the disc nucleus and a subsequent debulking can ease the resection of the herniated fragment. 3. Other technical tips (e) Partial pediculectomy Craniocaudal dimension of the lumbar vertebral foramen can be enlarged by removing the upper portion of the inferior vertebra’s pedicle. The starting point to carry out this partial pediculectomy becomes visible after resecting the base of the SAP: From the lateral and superior margin of the pedicle, the drilling with a diamond burr follows a medial and caudal direction until the upper third of the pedicle is resected (caudal limit), and the ligamentum flavum is exposed (medial limit). Based on the above description, when encountering patients in actual patient care, the patient group can be classified into eight subtypes as follows.

J.-H. Kim et al.

74

1. Most common patterns (a) Lumbar mono-radiculopathy from pure foraminal stenosis (from L2 to L5) (b) Lumbar dual-radiculopathy from foraminal stenosis and lateral recess stenosis (c) Lumbar foraminal stenosis at L5–S1 2. Others (a) Symptomatic foraminal stenosis + central stenosis (symptomatic vs asymptomatic) (b) Far-out syndrome (c) As a clinical setting, adjacent segment disease (ASD) (d) Considering issues—sagittal/coronal alignment, degree of slippage (e) Considering issues—medical comorbidities (Charlson Comorbidity Index, etc.) Across all the scenarios, to ensure a satisfactory outcome, when planning the surgical strategy the endoscopic surgeon must answer four main questions: 1 Which is the nerve root(s) responsible for the patient’s symptoms? 2 Where is that nerve root(s) compressed? 3 Which structure(s) is responsible for the compression? 4 Which kinds of tandem instability are related to the clinical symptoms?

After knowing the answers to the above questions and identifying which subcategory the patient in need of treatment belongs to, the remaining task is to establish a surgical treatment plan. The subsequent steps are simple, as it has become more clear what the problem is. Here, the author would like to explain the LUKE algorithm of endoscopic surgery for foraminal stenosis/lateral recess stenosis (Fig. 2). First, if there is only pure foraminal stenosis and symptoms of radiculopathy matching the corresponding exiting nerve root, TELF is performed. If these patients are accompanied by dominant disc herniation and are accompanied by symptoms, TELD (Transforaminal endoscopic lumbar discectomy) can be performed together with TELF. Also, if lateral recess stenosis (LRS) is accompanied by foraminal stenosis, it is determined which lesion is more dominant, LRS or FS.  When LRS is the main lesion, IE-LRD (Interlaminar endoscopic lateral recess decompression) can be considered together with TELF, and when FS is main, TE-LRD (Transforaminal endoscopic lateral recess decompression) can be implemented with TELF in consideration of efficiency. If you have some surgical experience and can perform endoscopic procedure skillfully, by executing ICELF (Interlaminar contralateral lumbar foraminot-

LUKE Algorithm of endoscopic surgery for foraminal stenosis/Lat Recess Stenosis Level, L25

Pure foraminal stenosis

Combined foraminal stenosis

Combined foraminal stenosis

Disc herniation

Lateral recess stenosis

Dominant FS

TELF

Dominant disc hernia

TELF & TELD

Dominant FS

TELF & TE-LRD Advanced skill

As ASD

Dominant LRS

TELF & TE-LRD TELF & IE-LRD

Level, L5S1

Combined foraminal stenosis

Unstable

Pure foraminal stenosis Combined foraminal stenosis

TELF Lumbar Fusion ALIF/OLIF/TLIF/PLIF

ICELF

Far-out syndrome

Endoscopic decompression

Fig. 2  The LUKE algorithm of endoscopic surgery for foraminal stenosis/lateral recess stenosis

Transforaminal Endoscopic Lumbar Foraminotomy/Foraminoplasty

omy), contralateral foraminal decompression and ipsilateral lateral recess decompression can be achieved at the same time [16–18]. In the case of FS accompanying ASD, spinal stability should be evaluated and TELF is considered in case of stable, and lumbar interbody fusion is considered in case of unstable. (Unstable spine refers to cases with angular instability or prominent axial pain with an asymmetric coronal plane greater than 15°.) Lastly, in the case of L5–S1, it can be classified separately due to its special anatomical characteristics, but it is not significantly different from L2–5 in establishing a treatment plan. In the case of pure FS, consider TELF, and in case of combined FS accompanied by other pathology, consider fusion method. For far-out syndrome that can only be seen in L5–S1 level, endoscopic decompression is recommended. The transforaminal endoscopic approach allows a horizontal access angle to the foramen and a direct all-around view of the foraminal decompression using an angled magnified camera, avoiding excessive superior facet joint resection. Likewise, the tactile feedback from the fine instruments inserted in the working sheath under high-resolution camera visualization permits a safe and precise dissection of foraminal ligaments, perineural scarring, and neural structures. For this reason, more and more spine surgeons are trying the endoscopic approach, especially in Asia [19]. Different from the paramedian and inside-out technique, the transforaminal approach utilizes the triangular working zone’s hypotenuse to achieve a customized approach trajectory for each patient when starting the procedure. The learning curve in endoscopy cannot be ignored, the mentorship and proctorship methods are recommended in training. Furthermore, it is essential to develop surgical skills and proficiency under the appropriate indications with patients carefully selected are the prerequisite for safe and effective endoscopic treatment. The low invasiveness and low intraoperative complications of endoscopic surgery make it possible to convert endoscopic surgery to day surgery in the future gradually. In the past few decades, the field of endoscopic spine surgery has achieved techno-

75

logical advancement [20]. With the advancement of image-assisted technology, augmented reality and robotics will further expand the indications for endoscopic surgery while ensuring safety and effectiveness of the procedure. Furthermore, with better government policy and insurance in the healthcare system, the cost of endoscopic surgery could be reduced, increasing the number of patients and physicians adopting it. Endoscopic decompression (LRD/ Foraminotomy) may be an excellent tool for alleviating pain. It offers a more powerful and less morbid alternative approach to spinal pathology that ultimately elevates the standard of care. This technique may be an excellent procedure for patients who are not willing to get lumbar fusion.

3 Case Illustration Case 1. A 66-year-old male, who had undergone posterior lumbar interbody fusion, L4–5 4  years ago, presents with Lt. leg radiating pain that had occurred 1 year ago. Endoscopic foraminotomy, L3–4, Lt. was performed (Figs. 3, 4, and 5). Clinical outcome (Visual Analog Scale for back/ leg pain) improved from 0/8 points before surgery to 0/0 points at 3  weeks, 2/0 points at 3  months, 4/2 points at 8  months, and 2/0 points at 2 years after surgery. Case 2. A 64-year-old male presents with Lt. leg radiating pain that had occurred 2 years ago. Endoscopic foraminotomy, L5–S1, Lt. was performed (Figs. 6, 7, and 8). Clinical outcome (Visual Analog Scale for back/ leg pain) improved from 2/5 points before surgery to 3/0 points at 1 month after surgery. Case 3. An 84-year-old female presents with Rt. leg radiating pain that worsened 4 months ago. Endoscopic foraminotomy, L4–5, Rt. was performed (Figs. 9, 10, and 11 and Video 1). Clinical outcome (Visual Analog Scale for back/ leg pain) improved from 0/7 points before surgery to 0/0 points at 1 month, 2 months, 2/0 points at 6 months, and 0/1 points at 23 months after surgery.

76

Fig. 3  Preoperative images. Collapse of disc due to ASD causing foraminal stenosis

Fig. 4  Comparison before and after surgery. Released Lt. L3 nerve root (star mark)

J.-H. Kim et al.

Transforaminal Endoscopic Lumbar Foraminotomy/Foraminoplasty

77

Fig. 5  Postoperative images. Successfully decompressed Lt. L3–4 foramen

Fig. 6  Preoperative images. Lt. L5–S1 foraminal bulging disc and hypertrophic facet joint causing foraminal stenosis

78

Fig. 7  Comparison before and after surgery. Released Lt. L5 nerve root (star mark)

Fig. 8  Postoperative images. It can be seen that the Lt. L5–S1 foramen was successfully decompressed

J.-H. Kim et al.

Transforaminal Endoscopic Lumbar Foraminotomy/Foraminoplasty

79

Fig. 9  Preoperative images. Gas-containing foraminal disc herniation and hypertrophic facet joint cause Rt. L4–5 foraminal stenosis

Fig. 10  Endoscopic view. After removal of foraminal ligaments, disc material, and cystic wall, Rt. L4 nerve root was released

80

J.-H. Kim et al.

Fig. 11  Postoperative images. Rt. L4–5 foramen has widened

MRI.  BMC Musculoskelet Disord. 2018;19(1):143. https://doi.org/10.1186/s12891-­018-­2064-­0. 9. Panjabi MM. The stabilizing system of the spine. Part II.  Neutral zone and instability hypothesis. J Spinal 1. Chen KT, Jabri H, Lokanath YK, Song MS, Kim Disord. 1992;5(4):390–6; discussion 7. https://doi. JS.  The evolution of interlaminar endoscopic spine org/10.1097/00002517-­199212000-­00002. surgery. J Spine Surg. 2020;6(2):502–12. https://doi. 10. Tacconi L, Signorelli F, Giordan E. Is full endoscopic org/10.21037/jss.2019.10.06. lumbar discectomy less invasive than conventional 2. Taylor H, McGregor AH, Medhi-Zadeh S, Richards surgery? A randomized MRI study. World Neurosurg. S, Kahn N, Zadeh JA, et  al. The impact of self-­ 2020;138:E867–E75. https://doi.org/10.1016/j. retaining retractors on the paraspinal muscles wneu.2020.03.123. during posterior spinal surgery. Spine (Phila Pa 1976). 2002;27(24):2758–62. https://doi. 11. Khandge AV, Sharma SB, Kim JS.  The evolution of transforaminal endoscopic spine surgery. org/10.1097/00007632-­200212150-­00004. World Neurosurg. 2021;145:643–56. https://doi. 3. Sihvonen T, Herno A, Paljarvi L, Airaksinen O, org/10.1016/j.wneu.2020.08.096. Partanen J, Tapaninaho A. Local denervation atrophy of paraspinal muscles in postoperative failed back 12. Ahn Y, Oh HK, Kim H, Lee SH, Lee HN. Percutaneous endoscopic lumbar foraminotomy: an advanced sursyndrome. Spine (Phila Pa 1976). 1993;18(5):575–81. gical technique and clinical outcomes. Neurosurgery. https://doi.org/10.1097/00007632-­199304000-­00009. 2014;75(2):124–33; discussion 32–3. https://doi. 4. Rantanen J, Hurme M, Falck B, Alaranta H, Nykvist org/10.1227/NEU.0000000000000361. F, Lehto M, et al. The lumbar multifidus muscle five years after surgery for a lumbar intervertebral disc 13. Ahn Y, Keum HJ, Lee SG, Lee SW.  Transforaminal endoscopic decompression for lumbar lateral recess herniation. Spine (Phila Pa 1976). 1993;18(5):568–74. stenosis: an advanced surgical technique and clinihttps://doi.org/10.1097/00007632-­199304000-­00008. cal outcomes. World Neurosurg. 2019;125:e916–24. 5. Gejo R, Matsui H, Kawaguchi Y, Ishihara H, https://doi.org/10.1016/j.wneu.2019.01.209. Tsuji H.  Serial changes in trunk muscle performance after posterior lumbar surgery. Spine 14. Lee HY, Ahn Y, Kim DY, Shin SW, Lee SH.  Percutaneous ventral decompression for (Phila Pa 1976). 1999;24(10):1023–8. https://doi. L4-L5 degenerative spondylolisthesis in mediorg/10.1097/00007632-­199905150-­00017. cally compromised elderly patients: technical case 6. Singh R, Yadav SK, Sood S, Yadav RK, Rohilla report. Neurosurgery. 2004;55(2):435. https://doi. R.  Magnetic resonance imaging of lumbar trunk org/10.1227/01.neu.0000130040.07472.dc. parameters in chronic low backache patients and healthy population: a comparative study. Eur Spine 15. Schubert M, Hoogland T. Endoscopic transforaminal nucleotomy with foraminoplasty for lumbar disk herJ. 2016;25(9):2864–72. https://doi.org/10.1007/ niation. Oper Orthop Traumatol. 2005;17(6):641–61. s00586-­016-­4698-­7. https://doi.org/10.1007/s00064-­005-­1156-­9. 7. Katsu M, Ohba T, Ebata S, Oba H, Koyama K, Haro H.  Potential role of paraspinal musculature 16. Kim HS, Kim JY, Wu PH, Jang IT. Effect of dorsal root ganglion retraction in endoscopic lumbar decompresin the maintenance of spinopelvic alignment in sive surgery for foraminal pathology: a retrospective patients with adult spinal deformities. Clin Spine cohort study of interlaminar contralateral endoscopic Surg. 2020;33(2):E76–80. https://doi.org/10.1097/ lumbar foraminotomy and discectomy versus transfoBSD.0000000000000862. raminal endoscopic lumbar foraminotomy and discec8. Katsu M, Ohba T, Ebata S, Haro H.  Comparative tomy. World Neurosurg. 2021;148:e101–e14. https:// study of the paraspinal muscles after OVF between doi.org/10.1016/j.wneu.2020.12.176. the insufficient union and sufficient union using

References

Transforaminal Endoscopic Lumbar Foraminotomy/Foraminoplasty 17. Chen KT, Song MS, Kim JS. How I do it? Interlaminar contralateral endoscopic lumbar foraminotomy assisted with the O-arm navigation. Acta Neurochir. 2020;162(1):121–5. https://doi.org/10.1007/ s00701-­019-­04104-­y. 18. Kim JY, Kim HS, Jeon JB, Lee JH, Park JH, Jang IT. The novel technique of uniportal endoscopic interlaminar contralateral approach for coexisting L5-S1 lateral recess, foraminal, and extraforaminal stenosis and its clinical outcomes. J Clin Med. 2021;10(7) https://doi.org/10.3390/jcm10071364.

81

19. Kim J-S, Yeung A, Lokanath YK, Lewandrowski K-U.  Is Asia truly a hotspot of contemporary ­minimally invasive and endoscopic spinal surgery? J Spine Surg. 2020;6(Suppl 1):S224–S36. https://doi. org/10.21037/jss.2019.12.13. 20. Akbary K, Kim J-S.  Recent technical advancements of endoscopic spine surgery with disparate or disruptive technologies and patents. World Neurosurg. 2021;145:693–701. https://doi.org/10.1016/j. wneu.2020.07.058.

Anterior Percutaneous Endoscopic Cervical Discectomy Yong Ahn, Han Joong Keum, and Shih-Min Lee

1 Introduction The standard surgical option for cervical disc herniation (CDH) causing radiculopathy is anterior cervical discectomy and fusion (ACDF), which has been regarded as a reliable procedure with acceptable fusion rates [1–14]. However, the following considerable peri- or postoperative complications may interfere with patients’ return to their ordinary life: (1) access problems, e.g., hematoma, dysphagia, hoarseness, and esophageal damage [15, 16]; (2) graft-related events, e.g., loss of disc height and nonunion [17–20]; and (3) adjacent segment disease [21, 22]. Since Kambin [23] and Hijikata [24] first described the posterolateral percutaneous discectomy technique, full-endoscopic discectomy techniques have been developed for the treatment of soft disc herniation in the lumbar spine [25–31]. The effectiveness of full-endoscopic lumbar discectomy has been proven in randomized controlled trials [32–38] and meta-analyses [39–47]. Percutaneous endoscopic cervical dis-

Y. Ahn Department of Neurosurgery, Gil Medical Center, Gachon University College of Medicine, Incheon, Republic of Korea H. J. Keum (*) · S.-M. Lee Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Republic of Korea

cectomy (PECD) has evolved as an efficient surgical option in adequately selected cases [48–57]. A ventral percutaneous approach using a small working channel endoscope enables spinal surgeons to reduce approach-related adverse events and extensive tissue trauma during open surgery. This article aimed to demonstrate a cutting-­ edge technique of anterior PECD for soft CDH.

2 Indications and Contraindications The surgical indications for anterior PECD are as follows: (1) soft CDH demonstrated on magnetic resonance imaging (MRI) and computed tomography (CT) scans; (2) cervical radiculopathy with or without axial neck pain and headache; (3) cervical myelopathy caused by soft CDH with a high risk of general anesthesia; and (4) sustained symptoms despite extensive nonoperative treatment for some period. The contraindications are as follows: (1) hard or calcified disc herniation, (2) sequestered or highly migrated disc herniation, (3) spondylosis with narrow disc space, (4) cervical myelopathy or ossification of the posterior longitudinal ligament, (5) segmental instability, (6) neurological or vascular pathologies mimicking a disc disease, and (7) workers’ compensation or litigation problems.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_10

83

84

3 Step-by-Step Technique The principal technique of anterior PECD for soft CDH consists of (1) a fluoroscopic-guided anterior percutaneous approach and (2) endoscopic-­ guided selective discectomy and foraminal decompression [58, 59].

3.1 Patient Preparation The patient is positioned supine, with the neck extended on a radiolucent table. The procedure can proceed with the patient under either general or local anesthesia. In the case of local anesthesia, adequate premedication with midazolam (0.05  mg/kg, intramuscularly) and fentanyl (0.8  μg/kg, intravenously) should be administered preoperatively.

3.2 Anterior Percutaneous Cervical Approach Under Fluoroscopic Guidance The primary principle of the surgical approach is an anterior percutaneous approach through the safe zone between the carotid vessels and trachea to the cervical disc. The anterior cervical anatomy is suitable for the anterior percutaneous approach. The vascular axis (including the carotid artery and vein) and visceral axis (including the trachea and esophagus) are separated by the deep fascia wall. Therefore, a safe working zone can be easily created using simple manual pressure between the vascular and visceral axes. The authors recommend using the contralateral access because it provides a better working space for the lateral zone of the disc. After confirming the operational level using anteroposterior and lateral fluoroscopic views, the surgeon palpates the carotid pulse and keeps it away from the surgical field. Then, the surgeon presses the zone between the carotid vessels and trachea with fingers, pushing the trachea to the contralateral side. When the surgeon feels the anterior surface of the disc via his/her fingertips, an 18-gauged approach needle is inserted into the disc space, directly from the mid-zone of the anterior disc

Y. Ahn et al.

surface to the target herniated disc fragment (Fig. 1a). Next, intraoperative discography is proceeded to stain the herniated disc and identify the leakage type with a mixture of indigo carmine and contrast media up to 0.5  mL.  A guidewire is introduced through the needle sheath into the disc, and a stab skin incision is created. After sequential dilation using dilators of different sizes, the final working sheath is placed to secure the surgical field of the herniated disc (Fig. 1b). A trephine can be inserted through the working sheath and cut into the annulus to reduce the intradiscal pressure and approach-related pain.

3.3 Selective Disc Decompression Under Endoscopic Visualization The actual performance of this step is selective removal of herniated fragments while preserving the central nucleus of the maternal disc. An ellipsoid working channel cervical endoscope is introduced through the working sheath, and the posterior disc space is identified under endoscopic visualization. The surgical space is continuously filled with antibiotic-containing normal saline at an irrigation rate of 30–40 mL/min. In the posterior subannular area, disc decompression is first performed to reduce the intradiscal pressure and create adequate working space. This initial decompression process should be conducted using endoscopic forceps and supplementary radiofrequency or a laser until the annular fissure of disc herniation is identified. Then, the annular anchorage is released using an endoscopic cutter or other devices until fibrotic adhesion is released, and the herniated fragment is released. The surgeon can identify and selectively remove the released disc fragment. After selective decompression, the epidural space and decompressed neural tissues can be seen through the opened annular fissure (Fig. 1c). The endpoint of the endoscopic surgery can be determined by solid pulsation and mobilization of the thecal sac and nerve roots (Fig.  1d). Postoperatively, the endoscope is withdrawn and a one-point subcutaneous suture with skin tape is

Anterior Percutaneous Endoscopic Cervical Discectomy

85

a

b

c

d

Fig. 1  Basic principle of anterior percutaneous endoscopic cervical discectomy. (a) An 18-gauged approach needle is inserted contralaterally through the safe zone between the carotid artery and trachea to the target point under fluoroscopic guidance. (b) After intraoperative discography, the final working sheath is placed at the posterior portion of the disc herniation point. (c) After the

adequate release of annular anchorage and fibrotic adhesion, the herniated fragment is removed using endoscopic forceps and supplementary devices. (d) The endpoint of the procedure can be determined by the strong pulsation and free mobilization of the neural tissue under an endoscopic view

applied. If there are no significant complications, the patient can be discharged within 24 h.

cal symptoms, and signs. Postoperative imaging studies should also be performed to check the adequacy of decompression and presence of complications.

4 Perioperative Consideration Preoperatively, the primary pathology should be determined precisely by performing thorough neurological examinations and radiographic studies, such as MRI and CT. Selective nerve root block can be used to confirm radiculopathy. Postoperatively, the patient’s condition should be assessed, including the pain status, neurologi-

5 Case Illustration A 47-year-old female patient had had severe neck pain and numbness in both arms for >1 year. She complained of concurrent headaches and interscapular pain. She also presented with decreased bilateral grasping power, without sensory defi-

Y. Ahn et al.

86

cits. The physical examination revealed bilateral positive signs on both the Lhermitte and Spurling tests. MRI and CT scans revealed central soft CDH compressing the spinal cord at the C4–5 level. The patient was recommended to undergo standard ACDF at this level. However, she refused open surgery because her occupation was a professional singer, and she was scared of vocal cord complications during surgery. Therefore,

she underwent anterior PECD under general anesthesia. Selective endoscopic discectomy was performed using the standard anterior PECD technique [58, 59] (Fig.  2a–d). Postoperatively, the patient’s pain and symptoms subsided immediately. There were no procedure-related complications, such as vocal cord palsy, dysphagia, or hematoma. Postoperative MRI showed satisfactory neural decompression. The patient returned

a

b

c

d

Fig. 2  Surgical procedure of anterior percutaneous endoscopic cervical discectomy in a 47-year-old female patient with soft cervical disc herniation at the C4–5 level. (a, b) An approach needle is inserted between the carotid artery and trachea. Note the endotracheal tube or tracheal air

shadow is pushed contralaterally by the surgeon’s fingertips, ensuring the safe working space in the fluoroscopic view. (c, d) After a working sheath is placed intradiscally, a selective discectomy is performed under endoscopic visualization

Anterior Percutaneous Endoscopic Cervical Discectomy

a

b

87

c

Fig. 3 Postoperative status of a 47-year-old female patient with soft cervical disc herniation at the C4–5 level. (a) Preoperative sagittal and axial images demonstrate an extruded disc compressing the spinal cord and nerve root. (b) Postoperative sagittal and axial images show a well-­ decompressed status immediately after the procedure.

Note the selective removal of the herniated disc while preserving the central nucleus. (c) The patient’s symptoms improved without any complications immediately. She could return to ordinary work within 1  month after surgery. Note the surgical scar is minimal without any skin suture

to everyday work within 1  month after surgery. At the 2-year follow-up evaluation, the global outcome of the patient was rated as excellent (Fig. 3a–c).

decompression under direct endoscopic visualization. The technical keys to success are as follows: (1) careful and firm pressure on the anterior neck securing a safe working zone between the carotid artery and trachea is essential to ensure an adequate surgical field; (2) a contralateral approach directing the target herniated fragment enables a selective discectomy without disruption of the central nucleus; (3) release of annular anchorage and fibrotic adhesion can make the discectomy easy and precise; and (4) the endpoint can be confirmed by free mobilization and pulsation of the thecal sac and nerve root in the endoscopic view. In conclusion, anterior PECD is effective for appropriately selected radiculopathy due to soft CDH.Conflicts of InterestNone.

6 Summary Currently, the standard surgical technique for CDH is ACDF.  However, conventional discectomy and fusion surgery can be too invasive for patients with radiculopathy due to soft CDH with a preserved disc height. Perioperative morbidity and long-term sequelae, e.g., adjacent disc disease, may reduce a patient’s quality of life. Therefore, anterior PECD is a minimally invasive alternative for soft CDH. This technique consists of two sequential procedures: (1) an anterior percutaneous cervical approach under fluoroscopic guidance and (2) selective endoscopic disc

Financial Disclosure  This study did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

88

References 1. Senter HJ, Kortyna R, Kemp WR.  Anterior cervical discectomy with hydroxylapatite fusion. Neurosurgery. 1989;25:39–42. 2. Bohlman HH, Emery SE, Goodfellow DB, Jones K. Robinson anterior cervical discectomy and arthrodesis for cervical rediculopathy. Longterm follow-up of one hundred and twenty-two patients. J Bone Joint Surg Am. 1993;75:1298–307. 3. Brigham CD, Tsahakis PJ. Anterior cervical foraminotomy and fusion. Surgical technique and results. Spine (Phila Pa 1976). 1995;20:766–70. 4. Cauthen JC, Kinard R, Vogler JB, Jackson DE, De Paz OB, Hunter OL, Wasserburger LB, Williams VM.  Outcome analysis of noninstrumented anterior cervical discectomy and interbody fusion in 348 patients. Spine (Phila Pa 1976). 1998;23:188–92. 5. Gore DR, Sepic SP. Anterior discectomy and fusion for painful cervical disc disease. Spine (Phila Pa 1976). 1998;23:2047–51. 6. Johnson JP, Filler AG, MacBride DQ, Batzdorf U.  Anterior cervical foraminotomy for unilateral radicular disease. Spine (Phila Pa 1976). 2000;25:905–9. 7. Laing RJ, Ng I, Seeley HM, Hutchinson PJ.  Prospective study of clinical and radiological outcome after anterior cervical discectomy. Br J Neurosurg. 2001;15:319–23. 8. Sonntag VK, Han PP, Vishteh AG. Aneterior cervical discectomy. Neurosurgery. 2001;49:909–12. 9. Papadopoulos EC, Huang RC, Girardi FP, Synnott K, Cammisa FP Jr. Three-level anterior cervical discectomy and fusion with plate fixation: radiographic and clinical results. Spine (Phila Pa 1976). 2006;31:897–902. 10. Shamsaldin M, Mouchaty H, Desogus N, Costagliola C, Di LN.  Evaluation of donor site pain after anterior iliac crest harvesting for cervical fusion: a prospective study on 50 patients. Acta Neurochir Wien. 2006;148:1071–4. 11. Fraser JF, Hartl R.  Anterior approaches to fusion of the cervical spine: a metaanalysis of fusion rates. J Neurosurg Spine. 2007;6:298–303. 12. Schroder J, Grosse-Dresselhaus F, Schul C, Wassmann H.  PMMA versus titanium cage after anterior cervical discectomy—a prospective randomized trial. Zentralbl Neurochirur. 2007;68:2–7. 13. Villavicencio AT, Pushchak E, Burneikiene S, Thramann JJ.  The safety of instrumented outpatient anterior cervical discectomy and fusion. Spine J. 2007;7:148–53. 14. Wright IP, Eisenstein SM.  Anterior cervical discectomy and fusion without instrumentation. Spine (Phila Pa 1976). 2007;32:772–4. 15. Pedram M, Castagnera L, Carat X, Macouillard G, Vital JM.  Pharyngolaryngeal lesions in patients undergoing cervical spine surgery through the anterior approach: contribution of methylprednisolone. Eur Spine J. 2003;12:84–90.

Y. Ahn et al. 16. Wang MC, Chan L, Maiman DJ, Kreuter W, Deyo RA.  Complications and mortality associated with cervical spine surgery for degenerative disease in the United States. Spine (Phila Pa 1976). 2007;32:342–7. 17. Kettler A, Wilke HJ, Claes L.  Effects of neck movement on stability and subsidence in cervical interbody fusion: an in  vitro study. J Neurosurg. 2001;94:97–107. 18. Tureyen K.  Disc height loss after anterior cervical microdiscectomy with titanium intervertebral cage fusion. Acta Neurochir (Wien). 2003;145:565–9. 19. Wilke HJ, Kettler A, Goetz C, Claes L.  Subsidence resulting from simulated postoperative neck movements. Spine (Phila Pa 1976). 2000;25:2762–70. 20. Epstein NE. A review of laminoforaminotomy for the management of lateral and foraminal cervical disc herniations or spurs. Surg Neurol. 2002;57:226–33. 21. Kulkarni V, Rajshekhar V, Raghuram L.  Accelerated spondylotic changes adjacent to the fused segment following central cervical corpectomy: magnetic resonance imaging study evidence. J Neurosurg. 2004;100:2–6. 22. Maiman DJ, Kumaresan S, Yoganadan N, Pintar FA.  Biomechanical effect of anterior cervical spine fusion on adjacent-segments. Biomed Mater Eng. 1999;9:27–38. 23. Kambin P, Sampson S.  Posterolateral percutaneous suction-excision of herniated lumbar intervertebral discs. Report of interim results. Clin Orthop Relat Res. 1986;207:37–43. 24. Hijikata S. Percutaneous nucleotomy. A new concept technique and 12 years’ experience. Clin Orthop. 1989;238:9–23. 25. Onik GM, Kambin P, Chang MK. Minimally invasive disc surgery. Nucleotomy versus fragmentectomy. Spine (Phila Pa 1976). 1997;22:827–8. 26. Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar disc herniation: Surgical technique, outcome, and complications in 307 consecutive cases. Spine (Phila Pa 1976). 2002, 27:722–31. 27. Ahn Y, Lee SH, Park WM, Lee HY.  Posterolateral percutaneous endoscopic lumbar foraminotomy for L5-S1 foraminal or lateral exit zone stenosis. Technical note. J Neurosurg. 2003;99(Suppl 3):320–3. 28. Ahn Y, Lee SH, Park WM, Lee HY, Shin SW, Kang HY.  Percutaneous endoscopic lumbar discectomy for recurrent disc herniation: surgical technique, outcome, and prognostic factors of 43 consecutive cases. Spine (Phila Pa 1976). 2004;29(16):E326–32. 29. Ahn Y. Transforaminal percutaneous endoscopic lumbar discectomy: technical tips to prevent complications. Expert Rev Med Devices. 2012;9(4):361–6. 30. Birkenmaier C, Komp M, Leu HF, Wegener B, Ruetten S. The current state of endoscopic disc surgery: review of controlled studies comparing full-endoscopic procedures for disc herniations to standard procedures. Pain Physician. 2013;16(4):335–44. 31. Ahn Y.  Percutaneous endoscopic decompression for lumbar spinal stenosis. Expert Rev Med Devices. 2014;11(6):605–16. 32. Mayer HM, Brock M. Percutaneous endoscopic discectomy: surgical technique and preliminary results

Anterior Percutaneous Endoscopic Cervical Discectomy

89

compared to microsurgical discectomy. J Neurosurg. 1993;78(2):216–25. 33. Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am. 1999;81(7):958–65. 34. Hoogland T, Schubert M, Miklitz B, Ramirez A. Transforaminal posterolateral endoscopic discectomy with or without the combination of a low-­dose chymopapain: a prospective randomized study in 280 consecutive cases. Spine (Phila Pa 1976). 2006;31(24):E890–7. 35. Ruetten S, Komp M, Merk H, Godolias G.  Full-­ endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine (Phila Pa 1976). 2008;33(9):931–9. 36. Ruetten S, Komp M, Merk H, Godolias G. Recurrent lumbar disc herniation after conventional discectomy: a prospective, randomized study comparing full-endoscopic interlaminar and transforaminal versus microsurgical revision. J Spinal Disord Tech. 2009;22(2):122–9. 37. Meyer G, Da Rocha ID, Cristante AF, et  al. Percutaneous endoscopic lumbar discectomy versus microdiscectomy for the treatment of lumbar disc herniation: pain, disability, and complication rate—a randomized clinical trial. Int J Spine Surg. 2020;14(1):72–8. 38. Gibson JNA, Subramanian AS, Scott CEH.  A randomised controlled trial of transforaminal endoscopic discectomy vs microdiscectomy. Eur Spine J. 2017;26(3):847–56. 39. Nellensteijn J, Ostelo R, Bartels R, Peul W, van Royen B, van Tulder M.  Transforaminal endoscopic surgery for symptomatic lumbar disc herniations: a systematic review of the literature. Eur Spine J. 2010;19(2):181–204. 40. Cong L, Zhu Y, Tu G.  A meta-analysis of endoscopic discectomy versus open discectomy for symptomatic lumbar disk herniation. Eur Spine J. 2016;25(1):134–43. 41. Li XC, Zhong CF, Deng GB, Liang RW, Huang CM.  Full-endoscopic procedures versus traditional discectomy surgery for discectomy: a systematic review and meta-analysis of current global clinical trials. Pain Physician. 2016;19(3):103–18. 42. Ruan W, Feng F, Liu Z, Xie J, Cai L, Ping A.  Comparison of percutaneous endoscopic lumbar discectomy versus open lumbar microdiscectomy for lumbar disc herniation: a meta-analysis. Int J Surg. 2016;31:86–92. 43. Ding W, Yin J, Yan T, Nong L, Xu N.  Metaanalysis of percutaneous transforaminal endoscopic discectomy vs. fenestration discectomy in the treatment of lumbar disc herniation. Orthopade. 2018;47(7):574–84. 44. Zhang B, Liu S, Liu J, et al. Transforaminal endoscopic discectomy versus conventional microdiscectomy for lumbar discherniation: a systematic review and meta-­ analysis. J Orthop Surg Res. 2018;13(1):169.

45. Barber SM, Nakhla J, Konakondla S, et al. Outcomes of endoscopic discectomy compared with open microdiscectomy and tubular microdiscectomy for lumbar disc herniations: a meta-analysis. J Neurosurg Spine. 2019:1–14. https://doi.org/10.3171/2019.6.SP INE19532. 46. Gadjradj PS, Harhangi BS, Amelink J, et  al. Percutaneous transforaminal endoscopic discectomy versus open microdiscectomy for lumbar disc herniation: a systematic review and meta-analysis. Spine (Phila Pa 1976). 2021;46(8):538–49. 47. Li WS, Yan Q, Cong L.  Comparison of endoscopic discectomy versus non-endoscopic discectomy for symptomatic lumbar disc herniation: a systematic review and meta-analysis. Global Spine J. 2022;12(5):1012–26. 48. Bonaldi G, Minonzio G, Belloni G, et al. Percutaneous cervical diskectomy: preliminary experience. Neuroradiology. 1994;36:483–6. 49. Siebert W. Percutaneous laser discectomy of cervical discs: preliminary clinical results. J Clin Laser Med Surg. 1995;13(3):205–7. 50. Hellinger J.  Technical aspects of the percutaneous cervical and lumbar laser-disc-decompression and nucleotomy. Neurol Res. 1999;21(1):99–102. 51. Chiu JC, Clifford TJ, Greenspan M, et al. Percutaneous microdecompressive endoscopic cervical discectomy with laser thermodiskoplasty. Mt Sinai J Med. 2000;67:278–82. 52. Lee SH, Gastambide D.  Perkutane endoskopische Diskotomie der Halswirbelsaule. In: Pfeil J, Siebert W, Janousek A, et  al., editors. Minimal-invasive Verfahren in der Orthopadie und Traumatologie. Berlin: Springer; 2000. p. 41–61. 53. Knight MT, Goswami A, Patko JT. Cervical percutaneous laser disc decompression: preliminary results of an ongoing prospective outcome study. J Clin Laser Med Surg. 2001;19:3–8. 54. Lee SH. Percutaneous cervical discectomy with forceps and endoscopic Ho:YAG laser. In: Gerber BE, Knight M, Siebert WE, editors. Lasers in the musculoskeletal system. Berlin: Springer; 2001. p. 292–302. 55. Ahn Y, Lee SH, Chung SE, Park HS, Shin SW. Percutaneous endoscopic cervical discectomy for discogenic cervical headache due to soft disc herniation. Neuroradiology. 2005;47(12):924–30. 56. Ahn Y, Lee SH, Shin SW.  Percutaneous endoscopic cervical discectomy: clinical outcome and radiographic changes. Photomed Laser Surg. 2005;23(4):362–8. 57. Lee JH, Lee SH.  Clinical and radiographic changes after percutaneous endoscopic cervical discectomy: a long-term follow-up. Photomed Laser Surg. 2014;32(12):663–8. 58. Ahn Y, Keum HJ, Shin SH. Percutaneous endoscopic cervical discectomy versus anterior cervical discectomy and fusion: a comparative cohort study with a five-year follow-up. J Clin Med. 2020;9(2):371. 59. Ahn Y.  The current state of cervical endoscopic spine surgery: an updated literature review and technical considerations. Expert Rev Med Devices. 2020;17(12):1285–92.

Full Endoscopic Posterior Cervical Spinal Surgery Ji Yeon Kim and Dong Chan Lee

1 Introduction Cervical radiculopathy is a degenerative spinal disease that leads to neck and arm pain, a typical symptom of nerve root compression caused by foraminal stenosis or intervertebral disc herniation [1]. When conservative treatment fails, surgical treatments, such as posterior cervical foraminotomy (PCF), anterior cervical discectomy with fusion, or disc replacement, are considered [1, 2]. PCF has gained popularity as an alternative to anterior cervical discectomy and fusion (ACDF) because it spares problems associated with fusion and surgical instrumentation [2, 3]. With the development of endoscopic spinal surgery, posterior endoscopic cervical foraminotomy (PECF) has shown favorable clinical outcomes, including those related to blood loss, operating time, and hospital stay, compared with open PCF surgery [2–5]. Endoscopic systems offer a multiaxial viewing angle and a magnified clear endoscopic view that enable detailed bone decompression using various approaches [6, 7]. Based on these advantages, advanced techniques

Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/978-­981-­19-­9849-­2_11.

for preserving the facet joint with its capsule have been developed for both types of endoscopic PCFs [4, 7, 8]. Cervical myelopathy is caused by degenerative cervical spondylosis, cervical disc protrusion, and cervical ossification of the posterior longitudinal ligament (OPLL). It usually requires surgical treatments, such as decompressive laminectomy, laminoplasty, ACDF, anterior cervical corpectomy, or anterior-posterior combined approaches, rather than minimally invasive approaches or endoscopic spinal surgery [9]. With the development of endoscopic spinal surgery, cervical myelopathy can be treated using an endoscopic posterior cervical approach, including full and biportal endoscopies [10, 11]. Full endoscopic spinal surgery has limitations in terms of the use of various instruments compared with biportal endoscopic surgery. However, with the development of a fine endoscopic diamond drill, delicate bone drilling can be performed over the dura without additional pressure on the spinal cord, and the ligamentum flavum can be removed as the final surgical step to avoid spinal cord injury due to early dural exposure. Furthermore, with cervical foraminal decompression, spinal canal stenosis can be treated simultaneously using a full endoscopic system.

J. Y. Kim · D. C. Lee (*) Department of Neurosurgery, Spine Center, Wiltse Memorial Hospital, Anyang, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_11

91

92

2 Indications and Contraindications 2.1 PECF Indications 1. Foraminal stenosis with or without foraminal disc herniation 2. Foraminal or lateral disc herniation, in which the main part of the herniated disc is located lateral to the lateral edge of the dural sac 3. Unilateral or bilateral cervical radiculopathy in a single cervical level 4. Unilateral radiculopathy in multiple cervical levels Relative Contraindications 1. Severe osseous foraminal stenosis at the C4–5 level owing to the risk of postoperative C5 palsy Contraindications 1. Combined symptomatic cervical canal stenosis with myelopathy 2. Combined prominent central disc herniation or OPLL 3. Definite segmental instability or cervical deformities

2.2 Posterior Endoscopic Cervical Decompressive Laminectomy (Laminotomy) Full endoscopic unilateral laminotomy for bilateral decompression can be considered for selected patients with one or two levels of cervical stenosis. Indications 1. Cervical canal stenosis due to hypertrophied ligamentum flavum with or without myelopathy 2. Cervical canal stenosis with unilateral concomitant foraminal stenosis or foraminal disc herniation 3. Cervical canal stenosis with OPLL in less than 50% of the spinal canal

J. Y. Kim and D. C. Lee

Relative Contraindications 1. Cervical canal stenosis involving more than three levels 2. Cervical canal stenosis with central disc herniation 3. Cervical level above C3–4 4. Cervical canal stenosis with bilateral concomitant foraminal stenosis or foraminal disc herniation 5. Cervical canal stenosis with prominent ossification of the ligamentum flavum Contraindications 1. Cervical canal stenosis with segmental instability 2. Cervical canal stenosis with OPLL involving more than 50% of the spinal canal 3. Cervical canal stenosis with prominent central disc herniation 4. Severe cervical canal stenosis with a higher risk of cervical cord injury If patients have combined symptomatic pathologies of cervical canal and foraminal stenoses, PCF and decompressive laminectomy should be performed simultaneously for complete neural decompression. Furthermore, in cases of contraindications, conventional ACDF or posterior cervical spinal surgery, such as laminoplasty or laminectomy, can be considered instead of the posterior endoscopic approach.

3 Step-by-Step Technique Various full endoscopic systems are used for PECF, as determined by the surgical approach and surgeon’s preference (Fig. 1).

3.1 Anesthesia and Position All surgeries are performed under general endotracheal anesthesia in the prone position on a chest bar. The head is fixed, and both shoulders are pulled by plasters. A gel-type facial pad should be used to protect the face and eyeballs from direct high-contact pressure. The neck is flexed, and the upper back is slanted down for

Full Endoscopic Posterior Cervical Spinal Surgery

a

b

Fig. 1  Operative position and surgical instruments. (a) Interlaminar endoscopic system with a 12° viewing angle, an 8.4-mm outer diameter, and a 120-mm length. Endoscopic diamond drills. (b) Small-diameter endo-

a

93

c

scopic system with a 30° viewing angle, 7.3-mm outer diameter, and 251-mm length. (c) Operative position with a facial pad and plaster

b

c

Fig. 2  Illustration of the two types of the full endoscopic posterior cervical approach for osseous foraminal stenosis on the axial plane. (a) The cervical exiting nerve root is severely compressed by the prominent bony spur and

hypertrophied facet joints on the left side of the cervical neuroforamen. (b) Conventional approach for PECF. (c) Inclined pedicular-vertebrotomy approach for PECF. PECF posterior endoscopic cervical foraminotomy

good venous return to reduce the risk of intraoperative bleeding. The abdomen is relaxed using an H-shaped pillow to avoid increasing the abdominal pressure (Fig. 1).

interlaminar (Fig. 1).

3.2 Surgical Approach PECF can be performed using two different techniques [i.e., conventional PECF and inclined pedicular-vertebrotomy (IPV)-PECF] according to the disease characteristics and surgeon’s preference (Figs. 2 and 3).

3.3 Full Endoscopic PCF (Conventional Approach) (Figs. 2b and 3b) Conventional PECF can be performed using any type of full endoscopic system, including the

or

transforaminal

approach

3.3.1 Skin Entry Point (Fig. 4) Under image intensification, fluoroscopic confirmation of the level is performed with the insertion of spinal needles into the target area. A 1-cm vertical skin incision is made on the uncovertebral joint line or more medial to the uncovertebral joint line on the anteroposterior (AP) C-arm image, which provides a lateral trajectory angle of 5–15°. On the lateral C-arm image, a skin incision is created on the lower endplate line of the involved disc space at the caudocranial approach angle. This cranial and lateral-directed surgical approach helps undercut the facet joint and preserve the inferior articular process (IAP). The target of needling is the junction of the lower margin of the target disc space and uncovertebral joint line.

J. Y. Kim and D. C. Lee

94

a

b

Fig. 3  Illustration of the two types of the full endoscopic posterior cervical approach for osseous foraminal stenosis on the sagittal plane. (a) The osseous cervical foraminal stenosis severely compresses and distorts the exiting

a

b

c

nerve root. (b) Conventional approach for PECF. (c) Inclined pedicular-vertebrotomy approach for PECF. PECF posterior endoscopic cervical foraminotomy

c

Fig. 4  Skin entry points for full endoscopic posterior cervical foraminotomy. (a) Skin entry is made on the medial pedicular border or more medial area (bold red line) instead of the UVJ line (green line). (b) A skin incision is created on the lower endplate line of the involved disc

space (red arrow line). A cranially made skin entry may cause excessive facet joint resection owing to the disadvantageous approach angle (green arrow line). (c) A more medially made skin entry helps undercut the facet joint. UVJ uncovertebral joint

3.3.2 Sequential Dilation and Working Cannula Insertion After serial dilations, a working cannula is inserted along the dilator to dock on the medial border of the facet joint under image intensification. Incidental instrument insertion into the interlaminar area can cause ligamentum flavum penetration and spinal cord injury. Therefore, the

working cannula should be docked onto bony structures, such as the facet joint or adjacent lamina, instead of the interlaminar window. Furthermore, aggressive scraping or dissection around the facet joint should be avoided to prevent undue active bleeding from the branch of the radicular artery.

Full Endoscopic Posterior Cervical Spinal Surgery

a

e

b

f

95

c

d

g

Fig. 5  Intraoperative endoscopic views of full endoscopic posterior cervical foraminotomy at the right C5–6 level. (a) Endoscopic positions for stepwise surgical procedures. (b) Drilling is initiated at the anatomical V-point (green curved line). (c) Drilling of the inferior border of the upper level lamina and IAP. (d) The medial part of the facet joint is removed using a diamond drill. (e) Medial directional endoscopic view after removing the medial

facet joint [endoscope position (a) in a]. (f) Lateral directional surgical view after moving the endoscope [endoscope position (b) in a]. The tip of the SAP (black arrow) and facet joint space (blue asterisk) are clearly identified. (g) Schematic image after medial facet joint resection. IAP inferior articular process, SAP superior articular process, LF ligamentum flavum

3.3.3 Soft Tissue Dissection and Anatomical Landmark Confirmation (Fig. 5, Video 1) After confirmation of the working cannula position on C-arm images, endoscopy is introduced along the working cannula with constant saline infusion using an irrigation pump system. A saline infusion pressure of 35–50 mmHg can be safely used before ligamentum flavum removal. The soft tissue is dissected using a radiofrequency (RF) probe to expose the medial part of the facet joint, lower border of the upper level lamina, upper boundary of the lower level lamina, and interlaminar window. The V-point is an anatomical landmark that should be identified prior to drilling.

distal ends of the ligamentum flavum are exposed. Bone drilling is extended craniocaudally until the foraminal border of the upper and lower level pedicles is confirmed. Laminar drilling is continued laterally to the medial facet joint.

3.3.4 Partial Laminotomy and Facet Joint Removal (Fig. 5, Video 1) Circumferential laminotomy is performed using a 3.5-mm endoscopic drill until the proximal and

3.3.5 Lower Level Lamina and Superior Articular Process (SAP) Broad Bone Drilling (Fig. 6, Video 2) Facet joint drilling extends along the facet joint space by undercutting the IAP while preserving the joint capsule. Broad bone drilling of the lower level lamina and SAP is performed while anticipating the extent of the bone covering the exiting nerve root, cranial part of the lower level pedicle, and lateral aspect of the dural sac. Bone drilling is continued until the inner cortical bone resembles a thin paper to confirm the contour of the pedicle and nerve root. The lateral endpoint of

J. Y. Kim and D. C. Lee

96

a

b

d

e

c

Fig. 6  Intraoperative endoscopic views of full endoscopic posterior cervical foraminotomy at the right C5–6 level. (a) Facet joint drilling is extended laterally along the joint space. (b) The medial half of the SAP, including the superior tip part (black asterisk), is exposed after IAP undercutting. (c) The exposed SAP and lower level lamina are removed via layer-by-layer drilling. (d) The exiting

nerve root and pedicle can be identified through the thinned inner cortical bone. (e) The cranial border of the lower level lamina is also drilled until the epidural space (red asterisk) is observed through the drilled lamina. IAP inferior articular process, SAP superior articular process, LF ligamentum flavum

SAP drilling is determined by exposing the lateral border of the lower pedicle.

3.3.7 Additional Decompression (Fig. 8, Video 3) If the exiting nerve root is still compressed by the herniated disc, bony spur, and adjacent pedicles, additional decompression, such as discectomy, bony spur drilling, and partial pediculotomy, is required. Decompression of the entire length of the exiting nerve root from the axilla to the distal foraminal area should be confirmed. The cranial and caudal endpoints of bony decompression are identified on the foraminal surfaces of the upper and lower level pedicles (Fig. 8). The lateral endpoint of SAP resection can be determined by exposing the lateral border of the lower level pedicle (Figs. 7h and 8). All bony decompression procedures should be completed before removing the ligamentum flavum to prevent neural injury.

3.3.6 Thinned Lamina and SAP Removal (Fig. 7, Video 3) The thinned inner cortical bone is elevated and detached from the dura and nerve root, and the bone flap is removed using forceps. The exiting nerve root and lateral border of the thecal sac are exposed, and thick peridural adhesions cover them. Subsequently, the thinned SAP is removed laterally using a 1-mm punch by undercutting the SAP along the exiting nerve root. According to the surgeon’s preference and pathological characteristics, partial drilling of the upper or lower level pedicles can be performed for sufficient neural decompression.

Full Endoscopic Posterior Cervical Spinal Surgery

a

e

b

97

c

f

d

g

Fig. 7  Intraoperative endoscopic views of full endoscopic posterior cervical foraminotomy at the right C5–6 level. (a, b) A thinned C6 laminar flap is elevated using a dissector. (b–e) After removal of the bone flap, the nerve root and dural sac covered with a thick peridural mem-

a

b

c

d

Fig. 8  After completion of bony decompression in full endoscopic posterior cervical foraminotomy at the right C5–6 level (a) and left C7–T1 level (b). Adequate neural compression can be confirmed by exposing the upper (white asterisk) and lower level pedicles (yellow asterisk).

h

brane are exposed (black asterisk: tip of the SAP). (f–h) The remaining SAP is removed from the tip to the base part using a 1.0-mm punch. SAP superior articular process, IAP inferior articular process, LF ligamentum flavum, ENR exiting nerve root

e

(c) After bony decompression, the nerve root is still compressed by the herniated disc. (d) Discectomy is performed while working the cannula protecting the nerve root. (e) The nerve root is completely relieved dorsally and ventrally. ENR exiting nerve root

98

J. Y. Kim and D. C. Lee

a

b

Fig. 9  Removal of the thick peridural adhesion band entrapping the ENR. The nerve roots are ultimately released after adhesion removal. (a) C5 nerve root. (b) C8 nerve root. ENR exiting nerve root

3.3.8 Ligamentum Flavum and Peridural Adhesion Removal (Fig. 9, Video 4) The lateral part of the ligamentum flavum is detached from the drilled laminar margin and removed using forceps and punches to decompress the exiting portion of the nerve root and lateral dural sac. If the severe peridural adhesion band entraps the nerve root, adhesion tissues should be removed to ensure complete neural decompression and free the course of the nerve root (Fig. 9).

3.3.9 Final Exploration and Closure Diffuse epidural bleeding is controlled using a hemostatic agent rather than an RF probe. After confirmation of the release of the nerve root and free dural pulsation, a closed drainage catheter is inserted, and the skin wound is closed. Appropriate positioning of the drainage catheter is critical for preventing postoperative hematomas. The catheter position is confirmed via intraoperative radiography before the completion of the operation (Fig. 10).

Full Endoscopic Posterior Cervical Spinal Surgery

a

99

b

Fig. 10  Position of the drainage catheter. (a) Appropriate position of the drainage catheter. The catheter tip should be placed around the facet joint on the intraoperative

radiograph. (b) The catheter tip is located away from the decompressed site, and the hematoma fills the decompressed space

3.4 IPV Approach for PECF

nerve root at the starting point that curves downward (Fig.  11e–g). Furthermore, the additional space created by removing the SAP base enables the working cannula to access the ventral and distal foraminal spaces.

IPV-PECF was developed to safely remove ventral foraminal lesions and expand the distal foraminal area in cases of severe osseous foraminal stenosis (Figs.  2c and 3c). This technique is essential for ventral foraminal decompression and pedicularvertebrotomy; however, the basic surgical steps are the same as those in conventional PECF.  In IPV-PECF, a small-diameter endoscope with a 30° viewing angle, 7.0–7.5-mm outer diameter, 4.5– 4.7-mm working channel is used for efficient access to the ventral foraminal portion (Fig. 1b).

3.4.1 Skin Entry Point A skin incision is made on the line 1 cm medial to the uncovertebral joint, which is a more medial point than that in conventional PECF. This medially created skin entry is essential for an inclined surgical approach with mediolateral directions along the facet joint space (Fig. 4). 3.4.2 Inclined Surgical Route (Fig. 11) The craniolateral part of the lower level lamina, including the superior aspect of the pedicle, is obliquely drilled to create space for endoscopic access. Through this space, an increased approach angle in the craniolateral direction can be made to view the wide distal foraminal area and decompress its space (Fig.  11a–d), through which the base of the SAP, where the SAP joins the pedicle, can be removed using a punch to release the

3.4.3 Inclined Vertebrotomy for Ventral Foraminal Decompression (Fig. 12, Video 5) The endoscope is tilted in the craniolateral direction, and the ventral foraminal area is accessed through the space created by inclined laminotomy and pediculotomy. The inclined surgical route and 30° endoscope facilitate a broad view of the lateral foraminal area, and most of the IAP is preserved. The bevel tip is docked in the nerve root axillary area while protecting neural structures. The protruding part of the pedicle is drilled to the same level as the vertebral body using a 3-mm diamond drill. The nerve root is retracted in an obliquely elevated pattern using the bevel of the working cannula to prevent excessive neural retraction. Subsequently, oblique vertebrotomy is performed to remove the bone spur and hypertrophied annulus, with stepwise drilling and repositioning of the working cannula. Over-resection of the pedicle and vertebrae can lead to instability. Pediculotomy should be carefully performed only to drill no more than 3–5-mm combined dimension of the pedicle and corpus, which is measured using a 3.0- or 3.5-mm diamond drill. Furthermore, oblique pediculotomy using an

J. Y. Kim and D. C. Lee

100

a

b

e

c

d

f

Fig. 11  IPV approach for full endoscopic posterior cervical foraminotomy. (a) The endoscopic position is adjusted for a more increased angle of the craniolateral direction. (b–d) An endoscopic view is obtained to visualize the wide distal foraminal area along the ENR. (e, f) The SAP base is removed along the pedicle border using a 1.0-mm

g

punch. (g) A downward course of the nerve root is observed after sufficient removal of the SAP base. IAP inferior articular process, SAP superior articular process, LF ligamentum flavum, IPV inclined pedicular-­ vertebrotomy, ENR exiting nerve root

a

b

c

d

e

f

g

h

Fig. 12 Inclined pedicular-vertebrotomy for ventral foraminal decompression. (a) Careful dissection is performed between the ENR and bony spur. (b–d) The superior portion of the pedicle is obliquely drilled to access the bony spur while protecting the nerve root using the bevel of the working cannula. (e–g) After oblique vertebrotomy,

the bony spur is exposed and removed via intimate drilling without violating the intervertebral disc. (h) The bony spur is sufficiently removed through the obliquely created space by inclined pedicular-vertebrotomy. ENR exiting nerve root

Full Endoscopic Posterior Cervical Spinal Surgery

inclined surgical approach can reduce the required amount of pediculotomy.

3.4.4 Complete Neural Decompression Confirmation (Fig. 13, Video 5) After IPV, the space between the SAP and nerve root is expanded. A 1-mm punch is smoothly inserted into this space, and the residual hypertrophied SAP is further removed using an undercutting pattern. After sufficient neural ­ decompression at 360°, the natural downward course of the nerve root is restored through the space created by IPV. 3.4.5 Effect of IPV on Facet Joint Preservation During IPV-PECF, an additional space is created to pass through the endoscopic system,

a

b

d

e

Fig. 13 After the inclined pedicular-vertebrotomy approach for full endoscopic posterior cervical foraminotomy. (a) The ENR and lateral dural sac are sufficiently decompressed. (b) The caudal border of the upper level pedicle is confirmed. (c) The caudal foraminal area is also

101

and the endoscope is used to access the foramen via the craniolateral surgical route. Based on the modified approach, both the ventral and dorsal foraminal areas are reached through a deeply created space, and the facet joint is saved as much as possible (Fig. 14). After partial vertebrotomy, a sufficient free space is obtained between the nerve root and the SAP to undercut the distal SAP.  Therefore, if the IPV approach is used, a remarkable expansion of the distal foraminal space is possible even in severe osseous foraminal stenosis without significantly sacrificing the facet joint (Fig.  14). Meanwhile, during conventional PECF without ventral decompression for severe osseous foraminal stenosis, excessive facet resection more commonly occurs to achieve sufficient neural decompression (Fig. 15).

c

wholly decompressed, including the cranial part of the lower level pedicle. (d, e) The distal part of the nerve root is clearly identified and confirms the restoration of the natural downward course. ENR exiting nerve root

J. Y. Kim and D. C. Lee

102

a

d

b

c

f

e

Fig. 14  Features of bony removal after the IPV approach for full endoscopic posterior cervical foraminotomy. (a, b) Postoperative three-dimensional CT images show the surgical route for the IPV approach (yellow arrows) and well-preserved facet joint (red asterisks). (c) The IPV procedures significantly expand the lower foraminal levels (blue arrow). (d) A preoperative CT image shows severe osseous foraminal stenosis at the C5–6 and C6–7 levels. (e) Mid- and distal foraminal areas are sufficiently

a

b

Fig. 15  Illustrated cases of excessive facet resection during full endoscopic posterior cervical foraminotomy without ventral decompression. (a) The lateral to medial directed approach induces more facet resection. (b, c)

g

expanded while preserving the facet joint (two yellow lines indicate the mid- and distal foraminal sagittal planes). Sagittal CT images of the mid-foraminal (f) and distal foraminal areas (g) show the contour of the bony decompression. The bony spur and superior pedicle are obliquely drilled (yellow arrows) to expand the foraminal width and height. IPV inclined pedicular-vertebrotomy, CT computed tomography

c

Although an inclined surgical approach is used, excessive facet resection is inevitable owing to the prominent bony spur

Full Endoscopic Posterior Cervical Spinal Surgery

3.5 Full Endoscopic Posterior Cervical Decompressive Laminectomy 3.5.1 Skin Entry Point and Working Cannula Insertion (Fig. 16) A skin incision is created between the midline and medial pedicle line on the AP C-arm image to perform bilateral decompression. Based on lateral radiographs, a skin incision is made on the plane of the involved intervertebral disc. A longitudinal linear skin incision of approximately 1.0– 1.5 cm, parallel to the muscle fiber, is critical for free movement of the endoscopic system to the contralateral side. Serial dilators are inserted through the skin incision site, and a working cannula is inserted along the serial dilators. 3.5.2 Soft Tissue Dissection and Anatomical Landmark Identification (Fig. 17, Video 6) The position of the needle, serial dilators, and working cannula is confirmed using intraoperative radiography. The working cannula is docked on bony structures instead of the interlaminar window to prevent spinal cord injury. The entire targeted lamina and interlaminar window should be exposed and clearly identified before bone drilling using an RF probe.

a

b

Fig. 16  Skin entry points of the full endoscopic posterior cervical approach for canal decompression and foraminotomy. (a) Skin entry should be made between the pedicle and spinous process (blue circle), closer to the midline (white dotted line). (b) Based on the lateral radiograph, the skin entry point is placed between the adjacent spi-

103

3.5.3 Marginal Upper and Lower Level Lamina Drilling (Figs. 17 and 18, Video 6) Partial laminotomy is performed along the interlaminar border of the upper and lower level laminas using a fine endoscopic drill until the proximal and distal free margins of the ligamentum flavum are exposed. The inner cortical bone of the lamina is drilled until it resembles a thin paper. Drilling the midline of the upper level lamina facilitates access to the contralateral side of the interlaminar area. Laminotomy is extended to the medial border of the contralateral facet joint. A 3.0-mm endoscopic drill enhances the delicate bony drilling in the contralateral corner. 3.5.4 Hypertrophied Ligamentum Flavum Detachment and Removal (Fig. 19, Video 6) After confirmation of the laminotomy area, the proximal and distal free margins of the ligamentum flavum are separated from the bony margins. Subsequently, the ligamentum flavum is detached from the laminotomy sites, and epidural dissection is performed using a fine dissector. The ligamentum flavum flap is removed using endoscopic forceps, and the remaining portion at the contralateral corner is removed using a 1.0-mm endo-

c

nous processes on the line of the lower endplate (white line) to access the spinal canal lesions (red circle zone). (c) Determining the skin entry point is critical to succeeding bilateral cervical canal decompression and additional foraminotomy

J. Y. Kim and D. C. Lee

104

a

b

c

d

e

f

Fig. 17  Intraoperative endoscopic views of full endoscopic posterior cervical decompressive laminotomy at the left C5–6 level. (a) After soft tissue dissection, the adjacent lamina, facet joint, and interlaminar window are exposed. (b, c) Ipsilateral laminotomy of the upper level lamina to expose the proximal end of the LF. (d) The midline lamina blocks the endoscopic view of the contralat-

eral interlaminar area. (e) The contralateral sublaminar space is exposed after the midline lamina is removed, and the laminotomy is continued until the contralateral facet joint is confirmed. (f) Illustration of unilateral laminotomy with bilateral decompression. IAP inferior articular process, SAP superior articular process, LF ligamentum flavum

scopic punch. The continuous saline infusion pressure in the spinal cord may increase the epidural pressure and induce spinal cord injury. The saline infusion pressure should be maintained below 30  mmHg after the removal of the ligamentum flavum. The dura is sufficiently

expanded, and free dural pulsation is confirmed. Epidural bleeding is controlled using a hemostatic agent and an RF probe. Therefore, a drainage catheter should be inserted to prevent postoperative epidural hematoma.

Full Endoscopic Posterior Cervical Spinal Surgery

105

a

b

c

d

e

f

Fig. 18  Intraoperative endoscopic views of full endoscopic posterior cervical decompressive laminotomy at the left C5–6 level. (a) Ipsilateral laminotomy of the lower level lamina to expose the distal end of the LF. (b, c) The contralateral interlaminar space is accessed after the midline lamina is removed, and the laminotomy is continued to the contralateral side. (d, e) The contralateral medial border of the SAP should be drilled for successful neural

decompression. (f) The drilled edges of the IAP and SAP are confirmed after completing contralateral bony decompression (black asterisk: SAP tip). (g) Illustration showing the circumferential laminotomy and secured hypertrophied LF in the bilateral interlaminar window. IAP inferior articular process, LF ligamentum flavum, SAP superior articular process

a

b

c

e

f

g

Fig. 19  Intraoperative endoscopic views of full endoscopic posterior cervical decompressive laminotomy at the left C5–6 level. (a) The boundary of the circumferential laminotomy and free end of the LF are observed. (b) The LF is detached from the bony margin. (c) Careful epidural dissection is performed. (d) The detached LF is removed using forceps. (e) The remaining LF at the con-

g

d

tralateral corner is removed using 1.0-mm punches or forceps. (f) An additional decompressed space is confirmed between the medial facet joint and lateral dural sac. (g) A completely released dural sac is confirmed. SAP superior articular process, IAP inferior articular process, LF ligamentum flavum

J. Y. Kim and D. C. Lee

106

4 Postoperative Considerations A neck brace is recommended 3–4  days after PECF.  It should be maintained for 2  weeks if excessive facet joint resection is observed on postoperative magnetic resonance imaging (MRI) or computed tomography (CT). Postoperative laminar stress fractures can occur after full endoscopic posterior cervical decompressive laminectomy; therefore, a neck brace should be maintained for 2  weeks after surgery. The patency of the drainage catheter should be checked periodically to prevent postoperative epidural hematoma, especially in patients undergoing posterior decompressive laminectomy. The drainage catheter is usually removed 24–48  h after confirming the drainage amount. If incidental durotomy occurs during endoscopic surgery, the hole should be repaired using a fibrin sealant patch, or microscopic surgery must be performed. The best rest is recommended for 3–4  days in these cases, and close observation of neurologic symptoms is essential (Fig. 20).

a

5 Illustrated Cases Case 1. A 36-year-old man presented with radicular pain in his left arm after 3 weeks of conservative treatment. The motor power of left elbow flexion decreased to grade 4 (out of grade 5). Preoperative MRI and CT revealed foraminal stenosis with a prominent bony spur and herniated disc at the left C5–6 level (Fig. 21). The patient underwent a full endoscopic PCF and discectomy. An IPV approach was used to remove the ventral foraminal bony spur and herniated disc (Video 8). Postoperatively, the arm pain resolved, and the arm weakness improved without any complications. Postoperative MRI revealed successful neural decompression. Furthermore, based on the CT images, the IPV approach yielded sufficient expansion of the distal foraminal part and increased the foraminal height while minimizing facet joint resection (Fig. 21). MRI: magnetic resonance imaging, CT: computed tomography, PCF: posterior cervical foraminotomy, IPV: inclined pedicular-vertebrotomy. Case 2. A 54-year-old man presented with posterior neck pain and radicular left arm pain that had persisted for 3  months and did not

b

Fig. 20  Dural tear case during full endoscopic posterior cervical foraminotomy. (a) A large dural tear occurred at the axillary part of the nerve root during discectomy. (b) The dural defect site is sealed using a fibrin sealant patch (Video 7)

Full Endoscopic Posterior Cervical Spinal Surgery

a

d

107

b

e

c

f

g

Fig. 21  Images of illustrated Case 1. (a, b) Preoperative T2-weighted axial and sagittal MRI showing foraminal stenosis with a herniated disc at the left C5–6 level (blue arrows). (c) Sagittal CT image showing a collapsed foraminal space caused by a bony spur (blue arrow) and hypertrophied SAP. (d, e) Postoperative MRI revealing sufficiently decompressed foraminal and lateral spinal

canals. (f) Based on the postoperative CT image, the bony spur is successfully removed through the space created by the inclined pedicular-vertebrotomy approach (red arrow). (g) Three-dimensional CT image showing the surgical trajectory (bold yellow arrow) and well-preserved facet joints (black asterisk). MRI magnetic resonance imaging, CT computed tomography, SAP superior articular process

respond to conservative treatment. The motor power of left elbow flexion gradually decreased to grade 3 (out of grade 5). Preoperative MRI and CT revealed severe osseous foraminal stenosis with a prominent bony spur at the left C5–6 level (Fig. 22). The patient underwent a full endoscopic PCF. The IPV approach was used to remove the ventral foraminal bony spur; however, ventral decompression was not performed because of a nerve root tear that occurred during facet drilling (Video 9). Postoperatively, the arm and neck pain resolved, and the arm weakness improved. Numbness and dysesthetic pain developed in the second finger. Although the ventral bony spur was not removed, postoperative MRI revealed successful neural decompression (Fig.  22). MRI: magnetic resonance imaging,

CT: computed tomography, PCF: posterior cervical foraminotomy, IPV: inclined pedicular-vertebrotomy. Case 3. A 43-year-old man presented with gradual progression of motor weakness in the lower extremities and upper back and left arm pain despite 2  years of conservative treatment. Preoperative MRI and CT showed bilateral canal stenosis and left foraminal stenosis at the C7–T1 level (Fig. 23). The patient underwent full endoscopic left unilateral laminotomy with bilateral decompression and additional left foraminotomy at the C7–T1 level. Postoperatively, neurologic deficits and arm pain improved significantly. Postoperative MRI and CT showed sufficient decompression of the bilateral spinal canal and left neuroforamen (Fig. 23). MR: magnetic resonance imaging, CT: computed tomography.

J. Y. Kim and D. C. Lee

108

a

b

c

d

e

f

g

h

i

j

Fig. 22  Images of illustrated Case 2. (a–d) Preoperative MR and CT images showing severe osseous foraminal stenosis with a prominent bony spur at the left C5–6 level (blue arrows). (e–h) Postoperative MR and CT images revealing sufficiently decompressed foraminal space after undercutting the facet joint and partial pediculotomy (red arrows), although the ventral bony spur was not removed.

k

l

(i) Three-dimensional CT image showing an inclined surgical trajectory (bold blue arrow) and a well-preserved facet joint. (j, k) Dural tear occurring at the root sleeve portion during facet drilling (black arrow). (l) The dural tear site was sealed using a fibrin sealant patch (black asterisk). MR magnetic resonance, CT computed tomography

Full Endoscopic Posterior Cervical Spinal Surgery

a

d

109

b

e

c

f

g

Fig. 23  Images of illustrated Case 3. (a–c) Preoperative MR and CT images showing bilateral cervical canal stenosis and left osseous foraminal stenosis at the C7–T1 level. (d–f) Postoperative MR and CT images revealing a sufficiently decompressed bilateral spinal canal and left neuroforamen (red and white dotted line: drilled border of bony structures). (g) The extent of laminotomy was con-

firmed using a postoperative three-dimensional spinal CT image (red arrowheads). Contralateral spinal canal decompression was performed through sublaminar drilling while preserving the spinous process and outer cortical bone (red-lined zone). MR magnetic resonance, CT computed tomography

6 Summary (Surgical Tips and Pitfalls)

6.2 Facet Joint Preservation During PECF

6.1 Posterior Endoscopic Surgical Approach

During PECF for severe osseous foraminal stenosis, additional compression to the involved nerve root is inevitable during punching of the distal part of the SAP because the nerve root is severely squeezed between the hypertrophied SAP and the prominent bone spur. Therefore, excessive facet resection of over 75% occasionally occurs for sufficient neural decompression while preventing serious neural compression injury. Additional compression of the vulnerable nerve root may cause motor weakness and a broader hypoesthesia area. Biomechanically, the facet joint limits the movement of the spinal motion segment, and excessive facet resection can lead to postoperative instability and mechanical neck pain.

The types of surgical approach are determined on the basis of the symptoms and characteristics of the pathologies. The conventional PECF approach resolves almost all foraminal degenerative pathologies. However, the IPV approach may be more helpful in expanding the distal foraminal area and foraminal height than the conventional approach in patients with severe osseous foraminal stenoses. If cervical foraminal stenosis is combined with symptomatic cervical canal stenosis, additional posterior decompressive laminectomy is necessary for complete neural decompression.

J. Y. Kim and D. C. Lee

110

More medial and caudal skin entry points enable the endoscope to access the foramen via the craniolateral surgical route. This inclined surgical approach facilitates oblique undercutting of the facet joint to minimize facet violation. Therefore, in cases of severe osseous foraminal stenosis, modification of the skin entry or the IPV approach is necessary for sufficient neural decompression while preserving the facet joint.

6.3 Incomplete Foraminal Decompression The most common cause of unfavorable outcomes is incomplete neural decompression. Confirming anatomical endpoints is essential to ensure sufficient neural decompression. The cranial and caudal endpoints are the foraminal surfaces of the upper and lower level pedicles. The lateral endpoint is the lateral border of the lower level pedicle after the removal of the SAP base. Sufficient bone removal from the facet joint and pedicle should be prioritized over facet preservation for complete neural decompression. Because postoperative segment instability is usually not induced, facet resection is more than 50%.

6.4 Spinal Cord Injury Prevention During Posterior Cervical Decompressive Laminectomy The compressed spinal cord is vulnerable and may be injured even with slight pressure exerted by instruments. If contralateral laminar drilling is performed after exposing the dura, the risk of dural tear and direct spinal cord injury might increase, even during a careful drilling procedure. Furthermore, continuous saline infusion pressure on the exposed dura may cause spinal cord injury. Therefore, it would be better to use over-the-top decompression, removing the ligamentum flavum as the last surgical step after completing the circumferential laminotomy.

Conflict of Interest  None. Disclosure of Funding  None.

References 1. Woods BI, Hilibrand AS.  Cervical radiculopathy: epidemiology, etiology, diagnosis, and treatment. J Spinal Disord Tech. 2015;28(5):E251–9. 2. Dodwad SJ, Dodwad SN, Prasarn ML, Savage JW, Patel AA, Hsu WK. Posterior cervical foraminotomy: indications, technique, and outcomes. Clin Spine Surg. 2016;29(5):177–85. 3. McAnany SJ, Kim JS, Overley SC, Baird EO, Anderson PA, Qureshi SA.  A meta-analysis of cervical foraminotomy: open versus minimally-invasive techniques. Spine J. 2015;15(5):849–56. 4. Kim JY, Kim DH, Lee YJ, Jeon JB, Choi SY, Kim HS, et al. Anatomical importance between neural structure and bony landmark: clinical importance for posterior endoscopic cervical foraminotomy. Neurospine. 2021;18(1):139–46. 5. Ruetten S, Komp M, Merk H, Godolias G.  Full-­ endoscopic cervical posterior foraminotomy for the operation of lateral disc herniations using 5.9-mm endoscopes: a prospective, randomized, controlled study. Spine (Phila Pa 1976). 2008;33(9):940–8. 6. Kim HS, Wu PH, Lee YJ, Kim DH, Kim JY, Lee JH, et al. Safe route for cervical approach: partial pediculotomy, partial vertebrotomy approach for posterior endoscopic cervical foraminotomy and discectomy. World Neurosurg. 2020;140:e273–82. 7. Song KS, Lee CW. The biportal endoscopic posterior cervical inclinatory foraminotomy for cervical radiculopathy: technical report and preliminary results. Neurospine. 2020;17(Suppl 1):S145–s153. 8. Kim JY, Hong HJ, Lee DC, Kim TH, Hwang JS, Park CK.  Comparative analysis of 3 types of minimally invasive posterior cervical foraminotomy for foraminal stenosis, uniportal-, biportal endoscopy, and microsurgery: radiologic and midterm clinical outcomes. Neurospine. 2022;19(1):212–23. 9. Heary RF, MacDowall A, Agarwal N. Cervical spondylotic myelopathy: a two decade experience. J Spinal Cord Med. 2018;42(4):1–9. 10. Shen J, Telfeian AE, Shaaya E, Oyelese A, Fridley J, Gokaslan ZL. Full endoscopic cervical spine surgery. J Spine Surg. 2020;6(2):383–90. 11. Kim J, Heo DH, Lee DC, Chung HT.  Biportal endoscopic unilateral laminotomy with bilateral decompression for the treatment of cervical spondylotic myelopathy. Acta Neurochir (Wien). 2021;163(9):2537–43.

Transforaminal Endoscopic Thoracic Discectomy and Decompression Junseok Bae

1 Introduction Thoracic disc herniation is rare compared with lumbar disc or cervical disc herniation, accounting for 0.25–0.5% of disc disease [1–3]. However, the diagnosis of thoracic disc herniation is increasing with the development of diagnostic methods such as magnetic resonance images (MRI). In patients with symptomatic thoracic disc herniation, clinical manifestations can be dynamic and progressive. Progressive myelopathy or voiding difficulty, lower limb motor weakness, and patients with radiculopathy not responding to conservative therapy are candidates for decompression surgery. Traditional surgical approaches vary from laminectomy, transpedicular, transfacetal approach, lateral extracavitary approach, costotransversectomy, or transthoracic. These approaches have been performed successfully but approach-related complications are inevitable. Especially, it is very important to identify the entry level of the Magna radicular artery and avoid ligating it to prevent paraplegia caused by spinal cord infarction [4].

Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/978-­981-­19-­9849-­2_12. J. Bae (*) Department of Neurosurgery, Cheongdam Wooridul Hospital, Seoul, Republic of Korea

Overall, complications from open surgery are reported to occur in over 25% of patients [1]. Transforaminal endoscopic thoracic discectomy (TETD) can minimize the incidence of postoperative spinal instability by minimizing the resection of bone and joint tissue. It can be performed under local anesthesia and has a faster recovery than open surgery [1–3, 5]. In addition, there is little traction on the nerve, which can reduce nerve edema, and it does not cause excessive nerve tissue exposure thus minimizing postoperative neural adhesion. Indications for endoscopic discectomy are becoming increasingly widespread due to patient needs and the development of endoscopic devices.

2 Indications Symptomatic soft disc herniation of paramedian, foraminal, or central disc space –– Condition that failed to improve symptoms after intensive conservative treatment including transforaminal epidural block and physical therapy. –– Calcified disc herniations, concomitant ossification of the posterior longitudinal ligament (OPLL) or ossification of the ligamentum flavum (OLF), significant myelopathy causing prominent neurological deterioration were excluded.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_12

111

J. Bae

112

3 Surgical Technique

rigid or articulating forceps either up biting or down biting figures. The jaws can be serrated or non-serrated. Radiofrequency probes can be used as a dissector and coagulator of soft tissue.

3.1 Step 1. Set Up 3.1.1 Instrument Although the basic mechanics of instruments for the thoracic transforaminal endoscopy system is very similar to the lumbar endoscopy system, the subtle variations in angles, diameters, and length of instruments hold the key to the successful execution of thoracic endoscopic surgery. 1. Thoracic endoscopes differ from other spinal endoscopes in the following ways (Fig. 1): (a) They are angled at 45°. This allows to work with a steeper access route and much shorter in length as the thoracic spine does not have much soft tissue cover dorsally [1–3, 5]. (b) They are smaller in diameter to accommodate space restriction in the thoracic spine. 2. Endo-reamers/endo drills are available in various sizes and angles. They are used for undercutting the superior facet or removal of a part of the vertebral body. They can also be used to make a hole in the annulus and allow easy passage of the dilator. They can also be used for the removal of small osteophytes or calcified disk material (Fig. 2). 3. Instruments for discectomy are endoscopic forceps and dissecting instruments. There are a

3.1.2 Position and Anesthesia The patient is positioned face down on a radiolucent operating table and on a Wilson frame, with the side to be operated on facing the surgeon. The arms are supported on arm boards over the head. As only mild sedation and local anesthesia are used, the extremities, buttocks, and shoulders can be prevented from jerking with tape if necessary. The marking of the level to be operated and the point of entry into the skin is made with the aid of C-arm images in the visualization and axial profile, corroborating the preoperative planning previously measured by computed tomography or magnetic resonance. Using the axial image of the level to be operated on, draw a line from the center of the protrusion through the edge of the facet joint and extend to the skin, joining another line drawn from that point to the midline. After the patient’s position, the surgeon faces the side to be operated on, the assistant nurse stands on the surgeon’s right side, and next to her the table with the instruments. Video tower, C-arm, and laser generator are on the other side of the patient, facing the surgeon. All procedures were performed under local anesthesia with conscious sedation (Fig. 3). b

3.1

120 1.5

1.5

5.8

45°

208/ 171

3.7 1.5

1.5

15°/30°

6.3

Fig. 1  Comparison of intraoperative view of 45° working angled thoracic endoscopy (a) and 15° lumbar endoscopy (b) used for TETD. Note endoscopic field of view (yellow) is wider with thoracic endoscopy

Transforaminal Endoscopic Thoracic Discectomy and Decompression

a

b

113

c

Fig. 2  Special surgical instrument used for foraminoplasty (a) manual bone drill, (b) manual bone reamer, (c) endoscopic high-speed burr Fig. 3 Intraoperative photo of operation theater. The surgeon and scrub nurse are standing on the left side C-arm machine and endoscopic monitor on its tower placed on the other side

3.2 Step 2. Skin Entry and Initial Needle Placement An appropriate skin entry point was determined by drawing a line from the posterior annulus at the mid-pedicular level to the lateral margin of facet join on axial CT scan cuts (Fig. 4). The skin entry point was commonly located at 5–6  cm from the midline. Although the scapular does move laterally with lifting arms, there is a limitation of the lateral access point. Extensive foraminotomy is thus required. The outline of foraminoplasty may be similar to other thoracic

levels. However, a more steep approach requires more aggressive techniques using reamers. On lateral fluoroscopic view, approach angle was measured by drawing an oblique line from the posterior endplate of the lower vertebra passing the tip of the superior articular process along with its inclination. This is to avoid a thick transverse process obstructing the working trajectory. After infiltration of local anesthetics, an 18-gauge needle is advanced along the planned trajectory under lateral fluoroscopic view to the lateral aspect of the superior facet. A guidewire was inserted through the needle. Epidurography

114

J. Bae

Fig. 4  The skin entry point was determined by drawing a line from the posterior annulus at the mid-pedicular level to the lateral margin of the facet joint on axial computed tomography scan or magnetic resonance imaging, usually located approximately 6–7 cm from the midline

was performed followed by an epidural block. Discography was performed by injecting a mixture of radiopaque dye (Telebrix; Guerbet, France), indigo carmine (Carmine; Korea United Pharmaceutical, Yoenki, Korea), and normal saline in a 2:1:2 ratio. Indio carmine stains the degenerated acidic nucleus blue and helps in identifying the herniated disc fragment.

3.3 Step 3. Foramioplasty and Decompression Foraminoplasty was performed using a serial dilating side cutting drill, reamer, or high-speed drill (Fig.  3). Alternative foraminoplasty techniques are (1) drilling the ventral aspect of the superior facet using a high-speed drill (Joimax® Shrill, 3.5  mm diamond burr) under direct endoscopic visualization, (2) using a Jamshidi needle to pass through the superior articular facet to reach the mid-pedicular level on AP fluoroscopic view. A guidewire was inserted through the needle followed by serial dilation with side cutting bone drill inserted over the wire [1, 2, 6]. A beveled 5.8 mm outer diameter

working cannula was then placed on the posterior disc space (Fig. 5). Then, the 3.1 mm endoscope (TESSYS thx, Joimax GmbH, Germany) was introduced. Under direct visualization, a blue-stained annular surface and herniated disc fragment could be identified. By removing the annulus of the outer layer and the internal layer of the posterior longitudinal ligament (PLL) with a sidefiring laser, the blue-stained herniated fragment was released from anchoring. Then the fragment was removed using microforceps (Video 1). Since thoracic disc herniation is mostly chronic and contained ­herniation with or without partial calcification, resection of PLL is not always necessary, and soft herniation decompression is the goal of surgery. After adequate decompression, ventral epidural space and thecal sac were visible (Fig. 6). Epidural pulsation can be observed even when the PLL remains. The authors use a sidefiring laser for TETD.  Holmium:yttriumaluminum-­garnet (Ho:YAG) laser (VersaPulse; Lumenis, Yokneam, Israel) was used to ablate the posterior annulus and the PLL with minimal thermal necrosis. Ho: YAG laser is effec-

Transforaminal Endoscopic Thoracic Discectomy and Decompression

a

115

b

Fig. 5  Fluoroscopic view of transforaminal working channel placement. Note that it is located on the medial pedicle line on the AP view (a) and the posterior vertebral line on the lateral view (b)

a

b

Fig. 6  Intraoperative photo showing (a) the posterior longitudinal ligament (arrow) and thickened posterior annulus and (b) full decompression of dural sac (*)

tive for (1) internal decompression within the posterior annulus at the initial stage, (2) shrinkage and resecting of the thickened posterior annulus around the annulus tear, (3) resecting of the PLL for exposing ventral epidural space for removal of transligamentous extrusion, and (4) resection of osteophyte or traction spur [2, 3].

4 Case Illustration Thirty-year old male presented with mid-thoracic back pain of 3 years duration. MRI thoracic spine showed left paramedian TDH at the T7–8 level. He underwent TETD under local anesthesia. Postoperatively patients showed significant improvement in both VAS and ODI scores.

J. Bae

116

a

b

d

c

Fig. 7  Preoperative MRI (a, b) shows left centrolateral soft disc herniation at the T7–8 level. Postoperative MRI (c, d) showing decompressed state at the T7–8 level. There is a small amount of irrigation fluid left in the disc space which is absorbed in a few days

Using modified Macnab’s criteria, the clinical outcome was categorized as good and it was maintained during 12 months of post-op followup (Fig. 7).

5 Complication Avoidance The proximity of major vascular, visceral, and neurological structures during TETD is a real concern [7]. Understanding of three-dimensional anatomy, sufficient experience with spinal endoscopy techniques, and expert patient selection to get optimum results. There is little risk but special caution is needed to prevent damage to the Adamkewickz artery, which is an important medullary artery, primarily located on the left side and is mostly branched between T9 and T11. When the segmental arteries are bifurcated from the intervertebral foramen to the radiculomedullary and intercostal branches, it is close to the lower portion of pedicle. Care should be taken

not to damage this part with reamer while doing foraminoplasty. To achieve a safe surgical trajectory into the spinal canal, foraminoplasty is an essential step. A safe corridor is mapped on the preoperative MRI to avoid the lung and the ribs. Another special consideration is given to the dural sac to spinal canal ratio. The needle trajectory for transforaminal aims to allow access as close as possible to the ventral surface of the dural sac avoiding injury of the dura mater. Reamer and bone drills allow removal of the ventrolateral portion of the superior facet to unveil the ventral pathology. Recurrent disc herniation is not uncommon but repeated TETD can be a surgical option. As in the case of recurrent disc herniation after transforaminal endoscopic lumbar discectomy, there is little epidural adhesion after TETD, repeated TETD is a safe procedure. In addition to the step-by-step surgical approach described above, there are some points to consider for the success and safety of endoscopic procedures.

Transforaminal Endoscopic Thoracic Discectomy and Decompression

a

b

c

d

e

f

117

h

i g

Fig. 8  Case presentation of 49-year-old female, presented with thoracic back pain and gait disturbance for a 3-year duration. Preoperative sagittal (a) and axial (b, d) MRI and CT scan (c, e) showing calcified disc herniation compressing the spinal cord at the T7–8 and T8–9 levels.

Transforaminal endoscopic discectomy under local anesthesia was done using a high-speed articulating burr to drill bone spur (g). Postoperative sagittal (f) and axial (h, i) MRI shows full decompression and the patient’s pain and myelopathy were improved

1. Neuromonitoring: Under general anesthesia, neuromonitoring including MEP and SSEP is essential. However, local anesthesia under conscious sedation provides “self-­neuromonitoring” by allowing patients to respond to stimuli. 2. Calcification: Preoperative CT scan should be checked to identify calcification. Up to 70% of thoracic herniated disks are reported to be calcified at presentation, and 5–10% of calcified discs are associated with an intradural extension [2, 8]. In case of severe epidural adhesion, calcified herniation carries a high risk of dural tear. Internal decompression or floating decompression should be considered as an alternative to total resection of calcified hernia (Fig. 8). 3. Giant herniation: Thoracic disc herniation occupies >40% of the spinal canal diameter and is frequently associated with myelopathy, calcification, intradural extension, and worse functional outcomes than those with smaller herniation. Care should be taken to avoid spinal cord compression during the procedure [9]. 4. Recurrent herniation: A recent largest clinical series reported 2.1% (2/98 patients) of recur-

rent herniation. There is least epidural adhesion after TETD.  Revision TETD can be performed safely [3]. 5. Incomplete decompression: Lack of visualization of the entire fragment is a common cause of incomplete decompression. The transligamentous hernia should be explored by resection of PLL to expose ventral dura mater. Otherwise, subligamentous decompression can leave the epidural fragment behind. Another common clinical scenario is related to central migrated hernia, where endoscopic visualization is restricted by limited endoscopic moving radius at the narrow neural foramen. Extensive foraminotomy/ foraminoplasty is necessary for highly migrated central disc herniation [10].

6 Summary Full endoscopic surgery is a safe and effective minimally invasive surgical option for thoracic pathology. Minimally invasive techniques have

118

brought a paradigm shift in the management of cervical/lumbar spinal conditions and similar techniques have been extrapolated to the thoracic region as well. With high-resolution visualization and a tissue-preserving surgical approach, endoscopic surgery enhances patient outcomes. One obstacle is the learning curve problem. With sufficient experience in cervical and lumbar spine endoscopic surgery, it will be possible to safely operate on the thoracic spine.

References 1. Gibson RDS, Wagner R, Gibson JNA.  Full endoscopic surgery for thoracic pathology: an assessment of supportive evidence. EFORT Open Rev. 2021;6(1):50–60. 2. Choi G, Munoz-Suarez D. Transforaminal endoscopic thoracic discectomy: technical review to prevent complications. Neurospine. 2020;17(Suppl 1):S58–65. 3. Bae J, Chachan S, Shin SH, Lee SH. Transforaminal endoscopic thoracic discectomy with foraminoplasty for the treatment of thoracic disc herniation. J Spine Surg. 2020;6(2):397–404.

J. Bae 4. Sharma SB, Kim JS. A review of minimally invasive surgical techniques for the management of thoracic disc herniations. Neurospine. 2019;16(1):24–33. 5. Bae J, Chachan S, Shin SH, Lee SH.  Percutaneous endoscopic thoracic discectomy in the upper and midthoracic spine: a technical note. Neurospine. 2019;16(1):148–53. 6. Wagner R, Telfeian AE, Iprenburg M, Krzok G, Gokaslan Z, Choi DB, et  al. Transforaminal endoscopic foraminoplasty and discectomy for the treatment of a thoracic disc herniation. World Neurosurg. 2016;90:194–8. 7. Sasani M, Fahir Ozer A, Oktenoglu T, Kaner T, Solmaz B, Canbulat N, et  al. Thoracoscopic surgery for thoracic disc herniation. J Neurosurg Sci. 2011;55(4):391–5. 8. Houra K, Saftic R.  Transforaminal endoscopic discectomy for large, two level calcified, thoracic disc herniations with 5-year follow-up. Neurospine. 2020;17(4):954–9. 9. Moran C, Ali Z, McEvoy L, Bolger C. Mini-open retropleural transthoracic approach for the treatment of giant thoracic disc herniation. Spine (Phila Pa 1976). 2012;37(17):E1079–84. 10. Quillo-Olvera J, Kim JS.  A novel, minimally invasive hybrid technique to approach intracanal herniated thoracic discs. Oper Neurosurg (Hagerstown). 2020;19(2):E106–16.

History and Basic Concepts of Unilateral Biportal Endoscopic Surgery (UBE) Dong-Geun Lee, Jae-Won Jang, and Choon-Keun Park

1 A History of Unilateral Biportal Endoscopic Surgery 1.1 The Inspiration, Initiation, and Innovations of Unilateral Biportal Endoscopic (UBE) Spine Surgery

technique shown in Fig. 1 used by Soliman was very similar to the UBE technique used today. The term “biportal” was first introduced in an article published in Korea in 2016 [7–10].

The idea of an endoscope originated from the use of Philipp Bozzini’s cystoscope for pediatric endoscopic neurosurgery in 1806 [1]. Direct endoscopic visualization of the spinal canal and its contents was born in 1931 from the pioneering work of Michael Burman [2]. Through the advent of both flexible fiberoptic light sources and optics for decades, the use and technique of standard arthroscopic instrumentation for spinal surgery were first reported in 1996 by De Antoni et  al. [3]. Two years later, they described clinical use of standard arthroscopic instruments for magnification, illumination, and irrigation [4]. Soliman reported surgical management of lumbar disc prolapse and spinal stenosis using two separate portals in 2013 and 2015 [5, 6]. The surgical

D.-G. Lee · J.-W. Jang · C.-K. Park (*) Department of Neurosurgery and Spine Center, Suwon Leon Wiltse Memorial Hospital, Suwon, Republic of Korea

Fig. 1  Intraoperative image showing an endoscope and arthroscopic shaver introduced through two separate portals

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_13

119

D.-G. Lee et al.

120

“Unilateral biportal endoscopy (UBE)” was also broadly used in a presentation entitled “Unilateral biportal endoscopic segmental sublaminoplasty for lumbar central stenosis” at the International Society of Minimally Invasive Spine Surgery (ISMISS) in Japan by Son Sang-Gu in 2013. Increased experience of endoscopic spine surgeons with UBE has led to an innovative explosion, mainly in Korea. As a result, Korean surgeons were able to apply the UBE technique to various pathologies such as cervical disc herniation and stenosis [11, 12], cervical spondylotic myelopathy [13], and thoracic ossification of the ligament flavum [14] known to be challenging. The UBE technique was also applied to relatively common applications such as lumbar disc herniation [15] or spinal stenosis [8], far-­lateral disc herniation [16], recurrent disc herniation [9], discitis, and abscess [17]. The biportal approach has enabled endplate preparation and foraminal decompression under direct visualization, which is vital for lumbar interbody fusion [18]. All major UBE-related papers published since 2016 have been published in Korea. This is attributed to Korea’s independent history of UBE. Currently, UBE is recognized as the most important endoscopic surgery of the spine. It can be applied to all areas of lumbar degenerative disease including fusion. It can also have been a

applied to the cervical and thoracic spine with favorable outcomes.

1.2 UBE History in Korea Abdul Gaffar presented an article entitled “Lumbar disc excision by midline extradural Endoscopy” at the 68th conference of American Academy of Orthopedic Surgeons (AAOS) in 2001. Korean Dr. Choi Young-Chul visited Abdul Gaffar in 2002 and began implementing UBE with Uhm Jin-Hwa for the first time in Korea (Fig. 2). In 2003, Uhm Jin-Wha presented an article entitled “Endoscopic lumbar discectomy for far-lateral disc herniation” and mentions the use of a biportal endoscope at the 4th Biennial Korea-Japan Conference on Spine Surgery in Japan. In 2013, Dr. Uhm and another Korean UBE pioneer Son Sang-Gu presented an article entitled “Unilateral biportal endoscopic segmental sub-laminoplasty for lumbar central stenosis” at the International Society of Minimally Invasive Spine Surgery (ISMISS) conference in Japan. In 2013, Son Sang-Gu presented another article entitled “The endoscopic unilateral laminectomy and bilateral decompression (ULBD), foraminotomy and fusion using UBE” at the International Intradiscal Therapy Society (IITS) conference in Korea (Fig. 3). Workshops on UBE led by Son Sang-Gu were held for the first time in Korea in 2013 (Fig. 4). b

Fig. 2 (a) Abdul Gaffar presenting in 2001, (b) Photograph of Abdul Gaffar (right) and Uhm. Jin-Hwa (Lt) in 2018

History and Basic Concepts of Unilateral Biportal Endoscopic Surgery (UBE) Fig. 3  Photograph of Gun Choi (left, President of International Intradiscal Therapy Society 2013) and Son Sang-Gu (right) in 2013

Fig. 4 (a) UBE Korean live surgery, (b) Seminar in 2014

a

b

121

D.-G. Lee et al.

122 Fig. 5 (a, b) Organization of the official UBE research society in 2017

a

b

In Korea, since 2002, independent trials and research related to UBE have been conducted. Full-scale presentations of research results and related workshops have been held since 2013. Based on these achievements, the UBE Research Society was organized in 2017 (Fig.  5). It has contributed to the development and populariza-

tion of UBE procedures through its academic activities. Through this active surgical technique and research, textbook publication of this society was accomplished in 2022 (Fig.  6). The unique history of UBE in Korea includes a background that has led to various research achievements and attempts related to UBE.

History and Basic Concepts of Unilateral Biportal Endoscopic Surgery (UBE)

Fig. 6  Textbook publication of UBE research society in 2022

123

124

2 Basic Concepts of Unilateral Biportal Endoscopic Surgery 2.1 Introduction Traditional open spine surgery requires surgeons to create about 3–4  in. of skin incision on the affected level of the spine and pull the paraspinal muscle and tissues using surgical retractors for maintaining the exposed surgical field. Despite optimal decompression and removal of pathologic lesions, wide open and retracted wounds might be related to persistent spinal back pain and poor functional outcomes caused by paraspinal soft tissues and facet joint injury [19, 20]. Open wound increases the risk for postoperative surgical site infection due to airborne particles and contaminated bone dusts developed by drilling. One of the most important points of spine surgery to reach favorable outcomes is successful completed decompression of neural component including spinal cord or nerve root. The introduction of a microscope in spine surgery makes it possible to achieve well visualization and magnification of surgical field, pathologies, and neural structure thus improving functional outcomes. However, microscopic spine surgery also requires open skin wound and paraspinal soft tissue dissection to expose the lesion [21]. Massive bleeding from ventral dural space or foraminal area can occur occasionally, which can disturb the visualization of pathologic lesions. Disturbance of visualization on pathologic lesions might be the cause of unfavorable outcomes related to incomplete decompression, dura injury, and neural structure injury. Minimal invasive spine surgery (MISS) has been developed to reduce paraspinal soft tissue damages and improve functional outcomes with early return to normal life. Using a tubular retractor and a microscope can reduce damage to the normal paraspinal tissue. However, technical difficulties caused by a restricted surgical field can damage neural tissue during operation [22]. It has

D.-G. Lee et al.

already been reported that neurologic complications and dural injuries are higher in MISS fusion than in conventional open fusion [13]. To become a popular surgical technique in MISS, the following points should be considered: (1) small incision and dissection to reduce paraspinal tissue damages, (2) magnified view of surgical field, (3) maintenance of a clean surgical field to distinct neural tissues and pathologic lesions, (4) no or low radiation exposure, and (5) closing operative field using a hole to reduce the possibility of infection. Learning curve is also a very important point to ensure reproducibility of surgery and establish a general spinal operative procedure. Percutaneous endoscopic spine surgery was first attempted by Kambin (1973) and Hijikata (1975). In this surgery, Kambin’s triangle as a working space is a very important zone for treating spinal disease. However, a lesion in the central spinal canal could not be easily treated through Kambin’s triangle [23]. Interlaminar approach using full endoscopy was developed by Ruetten with the advancement of spinal endoscopy and specific endoscopic instrument [24]. It is wildly adopted for lesions in central spinal canal, lateral recess, and foraminal area. Full-­ endoscopic spine surgery may be the most minimally invasive technique up to date. However, it has a very stiff learning curve. The demand for the development of new MISS techniques using spinal endoscopy is very high due to the abovementioned reasons. Unilateral biportal endoscopy (UBE) for lumbar spine was first described by De Antoni et  al. in 1996 [3]. Although UBE is not a full-endoscopic spine surgery, relatively early adaptation of this technique in beginners for spinal endoscopy might provide the advantages of an endoscopic spine surgery while overcoming the steep learning curve of a full-endoscopic spine surgery. The surgeon should know and understand several important concepts of UBE to maximize effects of this surgery. In this chapter, concepts of UBE with abovementioned valuable points will be discussed.

History and Basic Concepts of Unilateral Biportal Endoscopic Surgery (UBE)

2.2 Main Concepts of UBE 2.2.1 Minimal Invasiveness Concerns about minimally invasive spine surgery have increased to have better clinical outcomes and early return to normal life. Two small skin and fascial incisions within 1 cm are required to perform a UBE.  Serial muscle dilation is then required to make the working space for surgery. The spino-laminar junction of the pathologic level is the initial docking point of endoscopy and the serial dilators through the two portals in interlaminar approach. A fat-free space is generally located between the medial side of the multifidus muscle and lamina bone on the spino-laminar junction (Fig. 7). The interfascicular area between the two small bundles of multifidus makes some space with fat tissues. These two areas are important anatomical working space in a posterior interlaminar approach after atraumatic dissection in UBE. Minimal paraspinal tissue damage may lead to a significant reduction of immediate postoperative pain, opioid use, and hospital stay compared to conventional open surgery [25]. Facet joint violation during spine surgery is frequently needed to obtain an adequate decompression for the treatment of spinal stenosis. If decompression of spinal canal is not performed sufficiently, clinical outcomes will be poor due to remaining neurologic symptoms. Microscopic surgery offers a straightforward view of the operating area. About 30% of ipsilateral facet joint a

b

125

resection is required to reach optimal decompression of central spinal canal and lateral recess [20]. Excessive removal of facet joint can develop isthmic fracture, slippage increment, or instability of the operative level. UBE can reduce facet joint injury through undercutting or inclinatory resection of facet joint area. Moreover, fine handling of the endoscope and surgical instruments is possible through a movable channel surgery. It may reduce facet joint violation under a magnified and clean surgical view [21].

2.2.2 Fluid-Medium Surgery and Advantages Spinal endoscopic surgery is a fluid-medium technique through continuous saline irrigation. Irrigation saline enters from endoscopic portals and flows out through the working portal in UBE. There are four main advantages of continuous irrigation during UBE. First, fluent continuous saline irrigation maintains a clean operative field by washing out bone dust or other removed soft tissues. Second, the hydrostatic pressure on the working space can control the oozing from paraspinal soft tissues, exposed cancellous bone, and epidural venous plexus. Thus, continuous abundant saline irrigation and adjusted hydrostatic pressure on the working space can lead to clean operative views during UBE (Fig. 8). Third, hydrostatic pressure can help push the dura mater to the bottom and make a working space. It is especially helpful during the decompression of c

Fig. 7 (a) Working space on spino-laminar junction in interlaminar approach, (b, c) yellow areas in computed tomography and magnetic resonance imaging show free fat space between laminar bone and paraspinal muscle

126

Fig. 8 Clean operative image under well-controlled hydrostatic pressure and saline output

contralateral side in terms of obtaining a sufficient view of the surgical field [8]. Lastly, the rate of postoperative infection in microscopic surgery has been reported to be 4.4% in the modern antibiotic prophylactic era [26]. However, small skin incision and continuous irrigation in endoscopic spine surgery may reduce postoperative infection by prohibiting the contact of airborne particles and surgical working area. Therefore, fluid-­ medium UBE might also play an important role in decreasing the prevalence of postoperative infection.

2.2.3 Hydrostatic Pressure and Control Understanding and management of the hydrostatic pressure during UBE are very important. Surgeons can take advantage of hydrostatic pressure for controlling bleedings and making the working space. Bleeding from epidural venous plexus and exposed cancellous bone can be controlled under about 25  mmHg hydrostatic pressure. Therefore, hydrostatic pressure of about 30 mmHg under continuous irrigation is thought to be safe [7]. Some surgeons prefer natural maintenance of continuous irrigation with saline bag height of 40–50  cm from the working area because hydrostatic pressure is made 22  mmHg/30  cm gap of height between two

D.-G. Lee et al.

points (Fig. 9). Others use a saline pressure pump to maintain epidural pressure consistently. Usage of semicircular tube in working channel can help maintain abundant saline outflow. Surgeons have tried to understand the possibility of several complications associated with fluid. If the outflow is not maintained fluently, epidural pressure might be elevated and cause symptoms such as headache, intraocular hemorrhages, delayed awakening from anesthesia, and seizures [27]. Moreover, surgical field might not be maintained clearly due to congestion of epidural bleeding and bone dusts. If the outflow is not adequately made, irrigation saline can cumulate fluids in the extraperitoneal space or abdominal cavity, especially in the paraspinal approach due to the small working space of UBE.  Hypothermia may be developed due to the use of cold saline for a long time. The author recommends the use of mixed saline input systems from cold and warm saline bags, respectively.

2.2.4 View Magnification The development of spinal endoscopy has led to a high magnification of the operation field thus reducing the possibility of neural tissue and dura injury. Complete removal of pathologic lesions is also possible with the development of endoscopy and instruments, eventually leading to favorable clinical outcomes. Rough dissection between neural tissue and pathologic lesions under blurred surgical field might be associated with dura injury or neural tissue damage. Spinal endoscopy may take more magnified images compared to microscopy. It is very helpful for distinguishing normal area and pathologic area. Compared to microscopy, endoscopic camera or lens are located very close to pathologic lesions within the body. It can help magnify the lesion including spinal canal, contralateral side, foraminal area, and extraforaminal area under free handling of endoscopic location. Inserted cannula is lesser in UBE than in full-endoscopic surgery. However, the camera used has a larger diameter in UBE than in a full-endoscopic surgery. Therefore, the UBE endoscope has a lens with larger diameter compared to the lens in full-­ endoscopic surgery and it can provide more mag-

History and Basic Concepts of Unilateral Biportal Endoscopic Surgery (UBE)

127

Fig. 9  The distance between saline bag and operative field should be maintained at about 40–50 cm

nified and clean images of operative field during UBE surgery.

2.2.5 Free Handling of Spinal Instruments and Learning Curve Only two small holes are needed for endoscope and general surgical instruments, respectively. Free handling of general spinal instruments through working channel instead of working cannula is the main advantage of a UBE surgery. UBE interlaminar approach has similar surgical anatomy to a microscopic open surgery and instruments are also familiar to spine surgeons. On the other hand, full-endoscopic spine surgery is performed through small working cannula. Therefore, specially designed surgical instruments and surgical drills are used under angled endoscopic views. It makes that the beginners of full endoscopy may not be able to adapt easily to stiff learning curve [28]. The guidance of a non-dominant hand during surgery is very important to ensure a fine procedure. In microscopic surgery, the surgeon grasps the surgical suction in the non-dominant hand to focus on the lesion with removal of bone dust and bleeding. This guidance of non-dominant hand

during surgery also makes it possible to perform a fine surgical procedure through coordination of two instruments.

2.2.6 Triangular Formation Endoscope and surgical instruments should be docked with triangular formation (Fig.  10). Triangulation means that endoscope and general surgical instruments are very closely attached and located at the tip of each device. The maintenance of triangulation during the procedure can lead to clean images and view of magnifications for the target operated area. It makes it possible to freely handle surgical instruments without fighting between instruments and endoscope. If the patient is obese, the distance between the working portal and the endoscopic portal should be more than 3 cm to avoid early docking before reaching the target area. If the docking between the endoscope and surgical instruments is missed during surgery, the docking should be done again under C-arm guidance. 2.2.7 Operator Only Without Assistants Cost-effectiveness of newly developed procedure is a very important issue to become a successful

D.-G. Lee et al.

128

a

b

Fig. 10 (a, b) Triangulation between endoscope and surgical instrument

Fig. 11  Setting of operative room. Surgery can be performed by the operator and scrub nurse without any other assistants

treatment modality. Open or microscopic surgery needs an assistant to achieve well visualization of lesions or suck out blood during fine procedures. Nerve root retraction by a surgical assistant is also needed during a discectomy. However, most UBE procedures can be performed by the surgeon alone without a surgical assistant (Fig. 11). Although assistants may sometimes be required for a fine operating procedure, a robot arm may

replace the assistant in such situations. Reducing the number of people in an operating room is very important in future medical situations, especially in the Republic of Korea.

2.2.8 Usefulness and Riskiness of Radiofrequency Ablation Radiofrequency (RF) has been used in endoscopic spine surgery for disc ablation, soft tissue

History and Basic Concepts of Unilateral Biportal Endoscopic Surgery (UBE)

dissection, and bleeding controls. However, it may lead to nerve root injury due to heat when RF is used near a neural structure. An experimental study has shown that RF of 42 °C can lead to tissue changes in rat dorsal root ganglion, although this change is not permanent [29]. However, 80 °C heat can cause permanent neural tissue injury. Continuous use of RF wand can raise the temperature in the working space and cause permanent nerve damage [30]. When a surgeon uses an RF wand, short-term, brief use of the RF wand is recommended to avoid nerve root or dural injuries. RF use nearby a neural tissue is not recommended, especially in ablation power.

2.2.9 Radiation Exposure One of the main disadvantages is radiation exposure to the surgeon and patient in full-endoscopic spine surgery, especially in transforaminal endoscopic lumbar discectomy. However, radiation is only exposed during making working and endoscopic channels in UBE.  Because surgical ­anatomy is very similar to microscopic spine surgery, surgical procedures can be performed without additional c-arm radiographs. Reducing radiation exposure during UBE may play an important role to prevent complications related to radiation, especially in spine surgery. 2.2.10 Future of UBE: Expansion of Indications The use of microscope in spine surgery can improve surgical outcomes and reduce the rate of surgery-related complications. Therefore, microscopic spine surgery has been adopted and performed in entire fields of spine surgery including simple decompression, discectomy, fusion surgery, and intradural surgery with favorable outcomes and surgical reproducibility. Surgical cascade of UBE resembles that of a microscopic surgery except that it is a fluid-­ medium surgery with the usage of a free handling endoscope. UBE was first performed for cases with lumbar disc herniation or lumbar spinal stenosis in central spinal canal [3, 8]. Contralateral decompression and paraspinal lateral approach were then introduced and performed for foraminal lesions or extraforaminal lesions. Posterior

129

cervical foraminotomy using UBE has been performed 5 years ago with favorable outcomes [11]. Recently, cord-level decompression on cervical or thoracic spine was performed by some UBE pioneers [31]. UBE indications have been widely expanded to fusion surgery and fusion extension [18, 32]. Conclusively, UBE indications will increase as a microscopic surgery with the concept of MISS.

3 Conclusion UBE seems to be a feasible treatment option for various spinal disorders with the advantages of MISS, clean operative image, magnified view, and familiar to spine surgeon with free handling of surgical instruments. The previously mentioned advantages of UBE are very compelling to achieve goals of spinal surgery. To maximize the effect of UBE, surgeons need to understand the basic concepts of UBE.  In the future, research studies about UBE with high-level evidence should be performed and published to understand the superiority of an UBE over a microscopic surgery as the gold standard technique for treating spinal disorders.

References 1. Pettorini BL, Tamburrini G.  Two hundred years of endoscopic surgery: from Philipp Bozzini’s cystoscope to paediatric endoscopic neurosurgery. Childs Nerv Syst. 2007;23(7):723–4. 2. Burman MS.  Myeloscopy or the direct visualization of the spinal cord. J Bone Joint Surg. 1931;113:695–6. 3. De Antoni DJ, Claro ML, Poehling GG, Hughes SS.  Translaminar lumbar epidural endoscopy: anatomy, technique, and indications. Arthroscopy. 1996;12(3):330–4. 4. De Antoni DJ, Claro ML, Poehling GG, Hughes SS.  Translaminar lumbar epidural endoscopy: technique and clinical results. J South Orthop Assoc. 1998;7(1):6–12. 5. Soliman HM.  Irrigation endoscopic discectomy: a novel percutaneous approach for lumbar disc prolapse. Eur Spine J. 2013;22(5):1037–44. 6. Soliman HM.  Irrigation endoscopic decompressive laminotomy. A new endoscopic approach for spinal stenosis decompression. Spine J. 2015;15(10):2282–9.

130 7. Choi CM, Chung JT, Lee SJ, Choi DJ.  How I do it? Biportal endoscopic spinal surgery (BESS) for treatment of lumbar spinal stenosis. Acta Neurochir (Wien). 2016;158(3):459–63. 8. Eum JH, Heo DH, Son SK, Park CK.  Percutaneous biportal endoscopic decompression for lumbar spinal stenosis: a technical note and preliminary clinical results. J Neurosurg Spine. 2016;24(4):602–7. 9. Choi DJ, Jung JT, Lee SJ, Kim YS, Jang HJ, Yoo B.  Biportal endoscopic spinal surgery for recurrent lumbar disc herniations. Clin Orthop Surg. 2016;8(3):325–9. 10. Eun SS, Eum JH, Lee SH, Sabal LA. Biportal endoscopic lumbar decompression for lumbar disk herniation and spinal canal stenosis: a technical note. J Neurol Surg A Cent Eur Neurosurg. 2017;78(4):390–6. 11. Park JH, Jun SG, Jung JT, Lee SJ. Posterior percutaneous endoscopic cervical foraminotomy and diskectomy with unilateral biportal endoscopy. Orthopedics. 2017;40(5):e779–83. 12. Song KS, Lee CW. The biportal endoscopic posterior cervical inclinatory foraminotomy for cervical radiculopathy: technical report and preliminary results. Neurospine. 2020;17(Suppl 1):S145–53. 13. Kim JE, Yoo HS, Choi DJ, Park EJ, Jee SM. Comparison of minimal invasive versus biportal endoscopic transforaminal lumbar interbody fusion for single-level lumbar disease. Clin Spine Surg. 2021;34(2):E64–71. 14. Kang MS, Chung HJ, You KH, Park HJ. How I do it: biportal endoscopic thoracic decompression for ossification of the ligamentum flavum. Acta Neurochir (Wien). 2022;164(1):43–7. 15. Kim SK, Kang SS, Hong YH, Park SW, Lee SC.  Clinical comparison of unilateral biportal endoscopic technique versus open microdiscectomy for single-level lumbar discectomy: a multicenter, retrospective analysis. J Orthop Surg Res. 2018;13(1):22. 16. Park JH, Jung JT, Lee SJ. How I do It: L5/S1 foraminal stenosis and far-lateral lumbar disc herniation with unilateral bi-portal endoscopy. Acta Neurochir (Wien). 2018;160(10):1899–903. 17. Kang T, Park SY, Lee SH, Park JH, Suh SW. Spinal epidural abscess successfully treated with biportal endoscopic spinal surgery. Medicine (Baltimore). 2019;98(50):e18231. 18. Heo DH, Son SK, Eum JH, Park CK.  Fully endoscopic lumbar interbody fusion using a percutaneous unilateral biportal endoscopic technique: technical note and preliminary clinical results. Neurosurg Focus. 2017;43(2):E8. 19. Sihvonen T, Herno A, Paljarvi L, Airaksinen O, Partanen J, Tapanonaho A.  Local denervation atrophy of paraspinal muscles in postoperative failed back syndrome. Spine (Phila Pa 1976). 1993;18(5):575–81. 20. Guha D, Heary RF, Shamji MF.  Iatrogenic spondylolisthesis following laminectomy for degenerative

D.-G. Lee et al. lumbar stenosis: systematic review and current concepts. Neurosurg Focus. 2015;39(4):E9. 21. Heo DH, Lee DC, Park CK. Comparative analysis of three types of minimally invasive decompressive surgery for lumbar central stenosis: biportal endoscopy, uniportal endoscopy, and microsurgery. Neurosurg Focus. 2019;46(5):E9. 22. Lee GW, Jang SJ, Shin SM, Jang JH, Kim JD. Clinical and radiological outcomes following microscopic decompression utilizing tubular retractor or conventional microscopic decompression in lumbar spinal stenosis with a minimum of 10-year follow-up. Eur J Orthop Surg Traumatol. 2014;24(Suppl 1):S145–51. 23. Kambin P, Brager MD.  Percutaneous posterolateral discectomy. Anatomy and mechanism. Clin Orthop Relat Res. 1987;223:145–54. 24. Ruetten S, Komp M, Godolias G.  A new full-­ endoscopic technique for the interlaminar operation of lumbar disc herniations using 6-mm endoscopes: prospective 2-year results of 331 patients. Minim Invasive Neurosurg. 2006;49(2):80–7. 25. Park SM, Kim GU, Kim HJ, Choi JH, Chang BS, Lee CK, et al. Is the use of a unilateral biportal endoscopic approach associated with rapid recovery after lumbar decompressive laminectomy? A preliminary analysis of a prospective randomized controlled trial. World Neurosurg. 2019;128:e709–18. 26. Pull ter Gunne AF, Cohen DB. Incidence, prevalence, and analysis of risk factors for surgical site infection following adult spinal surgery. Spine (Phila Pa 1976). 2009;34(13):1422–8. 27. Lin CY, Chang CC, Tseng C, Chen YJ, Tsai CH, Lo YS, et  al. Seizure after percutaneous endoscopic surgery-­incidence, risk factors, prevention, and management. World Neurosurg. 2020;138:411–7. 28. Wang B, Lu G, Patel AA, Ren P, Cheng I. An evaluation of the learning curve for a complex surgical technique: the full endoscopic interlaminar approach for lumbar disc herniations. Spine J. 2011;11(2):122–30. 29. Moritz AR. Studies of thermal injury: III. the pathology and pathogenesis of cutaneous burns. An experimental study. Am J Pathol. 1947;23(6):915–41. 30. Podhajsky RJ, Sekiguchi Y, Kikuchi S, Myers RR. The histologic effects of pulsed and continuous radiofrequency lesions at 42 degrees C to rat dorsal root ganglion and sciatic nerve. Spine (Phila Pa 1976). 2005;30(9):1008–13. 31. Kim J, Heo DH, Lee DC, Chung HT.  Biportal endoscopic unilateral laminotomy with bilateral decompression for the treatment of cervical spondylotic myelopathy. Acta Neurochir (Wien). 2021;163(9):2537–43. 32. Park MK, Park SA, Son SK, Park WW, Choi SH. Clinical and radiological outcomes of unilateral biportal endoscopic lumbar interbody fusion (ULIF) compared with conventional posterior lumbar interbody fusion (PLIF): 1-year follow-up. Neurosurg Rev. 2019;42(3):753–61.

Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis Sang-Kyu Son and Man Kyu Park

1 Introduction Traditionally, microscopic surgery is the gold standard surgical treatment for lumbar spine disease, including lumbar spinal stenosis (LSS) and lumbar disc herniation (LDH) [1]. However, the conventional posterior approach has disadvantages. For example, it is associated with a risk of postoperative back pain or instability and paraspinal muscle atrophy due to muscle dissection or retraction [2–4]. Recently, unilateral biportal endoscopy (UBE) has been widely used in decompression surgery for LSS and LDH [5–9]. Several studies have shown that UBE has favorable clinical and radiological outcomes and advantages for LSS and LDH treatment [8, 10, 11]. The main advantages of UBE are the availability of a familiar and magnified surgical view and the independent movement of an endoscope and other instruments during surgery [10, 12, 13]. These can help achieve complete neural decompression and improve neurological outSupplementary Information The online version contains supplementary material available at https://doi. org/10.1007/978-­981-­19-­9849-­2_14.

S.-K. Son · M. K. Park (*) Department of Neurosurgery, Parkweonwook Hospital, Busan, Republic of Korea

comes while preventing complications correlated with the conventional posterior approach. UBE is a less invasive procedure. Thus, it is associated with a lower level of postoperative back pain and volume of blood loss and a shorter length of hospitalization by preserving the facet joint and paraspinal musculoligamentous structures [14]. To perform lumbar decompression and discectomy safely and effectively via UBE, some surgical techniques must be considered at each surgical stage. This chapter assesses the surgical techniques of the posterior approach and the strategies for preventing complications in patients undergoing UBE for LSS and LDH.

2 Step-by-Step Technique 2.1 Concept of UBE UBE is an endoscope-assisted spinal surgery that requires a series of working spaces with potential spaces. The Son’s space is an important anatomical working space in UBE.  There are two potential spaces. One is the interfascicular space, which is located between the two small muscles of the multifidus (Fig.  1a). The other is the space containing fat and connective tissues located between the multifidus muscle and the lamina (Fig. 1b). If these two potential

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_14

131

S.-K. Son and M. K. Park

132

a

c

b

d

Fig. 1  Overview of Son’s space. One is the interfascicular space (asterisk), which is located between the two small muscles of the multifidus (white arrow) (a). The other is the space containing fat and connective tissues located

between the multifidus muscle and the lamina (white arrow) (b). The positioning of the endoscope and surgical instrument using Son’s space through each portals. Anteroposterior (c) and lateral fluoroscopic images (d)

spaces can be converted into a working corridor, UBE guarantees similar indications as conventional spinal surgery and achieves minimal invasiveness. Therefore, these two potential spaces should be used when establishing portals (Fig. 1c, d). UBE is a fluid-medium surgery, with an input of irrigating saline via the scopic portal and an output via the working portal. Therefore,

to prevent the risk of fluid-related complications, the use of a semi-tubular retractor (Fig. 2a), which can maintain water outflow, is recommended. The semi-tubular retractor has additional functions. That is, it can retract the upper small muscle of the multifidus and the nerve root if needed and can be an instrument guide (Fig. 2b, c).

Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis

a

b

133

c

Fig. 2  Semi-tubular retractor maintains continuous fluid output during operation (a). Semi-tubular retractor can retract the upper small muscle of the multifidus (b) and can be an instrument guide (c)

a

b

Fig. 3  Skin incision and docking point on the fluoroscopic anteroposterior view. The docking point (white circle) is the lower part of the cranial lamina. Two skin incisions (working portal: white line, scopic portal: red line) are established approximately 3 cm apart, with the

center being the lower part of the cranial lamina at the midline of the proximal and distal pedicles (dotted line) (a). Triangulation of the endoscopic sheath and the dilator. Anteroposterior fluoroscopic image (b)

2.2 Lumbar Spinal Stenosis

3 cm apart, with the center being the lower part of the cranial lamina at the midline of the proximal and distal pedicles (Fig. 3a). The incisions depend on the obesity of the patient. That is, in patients with obesity, a more lateral and wider skin incision may be required to better access the depths of the muscles. The dominant hand should be used for the working portal for instrument manip-

2.2.1 Skin Marking and Portal Establishment The docking point is the junction of the spinous process and the lower part of the cranial lamina in the anteroposterior view on C-arm fluoroscopy. Two skin incisions are established approximately

134

ulation and the non-dominant hand for the scopic portal for endoscopic viewing. If a multilevel surgery is planned, the cranial endoscopic portals can be used in the working portal for next-level decompression. A #15 blade is used to make an incision in the lumbosacral fascia, which is sufficient for the insertion of serial dilators and the endoscopic sheath. Under C-arm fluoroscopy, serial dilators are placed at the docking point via the working portal. Moreover, they must be inserted via the interfascicular space between the multifidus muscles with less resistance. Then, they are wanded from the medial to the lateral side to bluntly dissect the interfascicular space between the multifidus muscles from the docking point. This step can enlarge the working space required for surgery, and, thus, can minimize the risk of paraspinal muscle injury. Serial dilators are inserted via the scopic portal to the docking point. Finally, the dilator tip and the endoscopic sheath can make a triangulation above the docking point, and the portal locations are then confirmed on fluoroscopy (Fig.  3b). The semi-tubular retractor is inserted via the working portal, and the upper small multifidus muscle, which can be used as the initial working space, is retracted laterally (Fig.  2b). Triangulation of an endoscope and other surgical instruments with the semi-tubular retractor is important for visualizing the surgical field and for manipulating instruments with less motion and vision limitation (Fig. 2c).

2.2.2 Bone Working (Fig. 4 and Video 1) UBE decompression for LSS is based on the operative technique used in microscopic unilateral laminectomy for bilateral decompression. After confirming that both portals are placed appropriately, soft tissues are cleared away with a radiofrequency (RF) probe to expose the anatomical landmark of the inferior edge of the cranial lamina, junction of the spinous process and cranial lamina, and interlaminar space (Fig.  4a). Caution should be taken when identifying and protecting the facet joint capsules. Subsequently, with a high-speed burr (preferably a round cutting burr), the lower part of the ipsilateral cranial

S.-K. Son and M. K. Park

lamina is removed down to the ligamentum flavum (LF) precisely and progressively (Fig. 4b). The base of the spinous process is removed to secure the space for safe bone working with minimal vision and motion limitations, particularly in contralateral decompression (Fig.  4c). This step is undertaken to prevent thecal sac compression by the endoscope or instruments ­ during contralateral decompression. After the ipsilateral cranial lamina and the base of the spinous process are removed sufficiently, the midline LF gap, which is the midline anatomical landmark, is identified (Fig.  4d). Based on this gap, the extent of bone working can be assessed from the ipsilateral to the contralateral side. The lateral end of the laminotomy overlaps with the medial aspect of the facet joint, which should be preserved as far as possible for stability. Generally, the LF should be left intact until the end of bone working to reduce the risk of dural tear or neural injury. After sufficient bone working is performed on the ipsilateral side, contralateral decompression can be performed through the sublaminar approach. Thus, the LF should be separated from the contralateral lamina with a freer elevator (Fig. 4e). After detaching the LF from the lamina, a space is established for bone working on the contralateral side (Fig.  4f). Using a high-speed drill, the undersurface of the contralateral spinous process and the lamina are undercut from the base of the spinous process to the medial aspect of the facet joints at the contralateral side (Fig. 4g). Therefore, the base of the spinous process must be removed to establish the working space because this structure interrupts the manipulation of the endoscope or other surgical instruments. Simultaneously, bleeding from the cancellous bone of the base of the spinous process is encountered. Since bone bleeding causes postoperative hematoma, this should be controlled with bone wax. Cranial bone working is performed as far superiorly as the cranial end of the LF (Fig. 4h, i). If a surgeon wants to explore the exiting nerve root and foramen at the ipsilateral or contralateral side, cranial laminotomy must be performed to achieve adequate exposure.

Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis

135

a

b

c

d

e

f

g

h

i

Fig. 4  Serial sequence endoscopic images of the bone working in lumbar spinal stenosis. The anatomical landmark of the inferior edge of the cranial lamina, junction of the spinous process and cranial lamina, and interlaminar space (a). The lower part of the ipsilateral cranial lamina is removed down to the ligamentum flavum (LF) (b). The base of the spinous process is removed to secure the space for safe bone working in contralateral decompression (c). The midline LF gap (white circle), which is the midline anatomical landmark, is identified (d). The LF should be

separated from the contralateral lamina with a freer elevator (e). After detaching the LF from the lamina, a space is established for bone working on the contralateral side (f). The undersurface of the contralateral spinous process and the lamina are undercut from the base of the spinous process to the medial aspect of the facet joints at the contralateral side (g). Anatomical landmark for cranial bone working. Dotted line indicates cranial end of the LF of ipsilateral side (h) and contralateral side (i)

2.2.3 LF Resection (Fig. 5 and Video 2) After bone drilling is completed, the superficial layer of the LF is detached from the posterior surface of the caudal lamina using a freer elevator or pituitary forceps (Fig. 5a, b). A sweeping motion made using a freer elevator over the posterior surface of the caudal lamina facilitates the superficial layer of the LF detachment. After resecting the superficial layer of the LF, the upper portion of the caudal lamina and the medial aspect of the superior articular process (SAP) can be identified as a landmark for lateral decompression (Fig. 5c). Caudal laminotomy begins at the upper portion of the caudal lamina, continuing along the medial

margins of the SAP and detachment of the deep layer of the LF (Fig. 5d–f). Before detaching the LF at the cranial side, due to the abundance of epidural blood vessels, coagulation using a RF probe is important to prevent bleeding (Fig. 5g). Next, the cranial side of the LF is removed by releasing the attachments of the LF from the bone edges using a Kerrison rongeur or freer elevator (Fig.  5h, i). In cases of severe stenosis, dense adhesions between the hypertrophied LF and dura will cause dural tear if rapid attempts are made to remove the LF without a clear plane of separation established initially with a freer elevator. Therefore, cautious dissection of the plane

S.-K. Son and M. K. Park

136

a

b

c

d

e

f

g

h

i

j

k

Fig. 5  Endoscopic images showing the sequential steps of resection of the ligamentum flavum (LF) in lumbar spinal stenosis. Detachment of the superficial layer of the LF at ipsilateral side (a) and contralateral side (b). Exposure of the upper portion of the caudal lamina and the medial aspect of the superior articular process (SAP) (white dotted curved line) (c). Caudal laminotomy begins at the upper portion of the caudal lamina, continuing along the

medial margins of the SAP and detachment of the deep layer of the LF (d–f). Before detaching the LF at the cranial side (white arrow), coagulation using a radiofrequency probe is important to prevent bleeding (g). Detachment of the cranial side of the LF (h, i). Confirmation of complete decompression at ipsilateral (j) and contralateral side (k)

between the dura and the LF should be performed to reduce the risk of dural tear. This en bloc removal of the LF minimizes the usage of a Kerrison rongeur thereby preventing the risk of dural tear or neural injury. If the ipsilateral removal of the LF is completed, resection of the LF at the contralateral side can be performed, as described above.

After resecting the LF, the disc space and traversing nerve root can be identified. Failure to complete an adequate subarticular decompression may cause residual leg symptoms. At the end of decompression, a root retractor is used to confirm whether an adequate nerve root decompression has been achieved throughout (Fig. 5j, k).

Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis

2.3 Lumbar Disc Herniation 2.3.1 Skin Marking and Portal Establishment The method used for skin marking and portal establishment in lumbar disc herniation is similar to that utilized in lumbar spinal stenosis. 2.3.2 Bone Working and Partial LF Resection (Fig. 6 and Video 3) After confirming that both portals are placed appropriately, soft tissues are coagulated using an RF probe to expose the anatomical structure of the inferior edge of the cranial lamina and the interlaminar space (Fig.  6a). Next, the rotator

137

muscle, which is attached to the interior edge of the cranial lamina, can be located. Identification of the rotator muscle is an indispensable step in this procedure because drilling should be performed at the medial portion of the rotator muscle. Without this step, surgeons can resect too much facet joints and lose orientation. Subsequently, ipsilateral laminotomy can be performed, and a high-speed drill or Kerrison rongeur is used to remove the cranial lamina down to the LF (Fig.  6b). If adequate cephalad laminotomy is completed, the medial aspect of the facet joint, LF, and caudal lamina can be identified (Fig. 6c). Then, the superficial layer of the LF is detached from the posterior surface of

a

b

c

d

e

f

g

h

i

Fig. 6  Serial sequence endoscopic images of the bone working and partial ligamentum flavum resection in lumbar disc herniation. The anatomical landmark of the inferior edge of the cranial lamina (white dotted line) and interlaminar space (a). The lower part of the ipsilateral cranial lamina is removed down to the ligamentum flavum (LF) (b). After cephalad laminotomy, the medial aspect of the facet joint, LF, and caudal lamina can be identified (c). Detachment of the superficial layer of the LF (d). The

upper portion of the caudal lamina and the medial aspect of the SAP can be identified and used as a landmark for lateral decompression (white dotted line) (e). The upper portion of the caudal lamina is partially removed with a Kerrison rongeur, continuing along the medial margins of the SAP and partially detached deep layer of the LF (f–h). Identification of the disc space and the traversing nerve root (i)

S.-K. Son and M. K. Park

138

the caudal lamina using a freer elevator or pituitary forceps (Fig. 6d). After removing the superficial layer of the ipsilateral LF, the upper portion of the caudal lamina and the medial aspect of the SAP can be identified and used as a landmark for lateral decompression (Fig.  6e). The upper portion of the caudal lamina is partially removed with a Kerrison rongeur, continuing along the medial margins of the SAP and partially detached deep layer of the LF (Fig. 6f–h). This technique preserves most of the LF and decreases postoperative adhesion. Since the LF is a natural barrier to preventing postoperative fibrosis and adhesion, it should be preserved immediately, unless it obstructs anatomical orientation. Upon partial removal of the ipsilateral LF, the disc space and the traversing nerve root can be visualized appropriately (Fig. 6i).

2.3.3 Discectomy (Fig. 7 and Video 4) The nerve root is commonly stretched tautly over a disc herniation thereby making it difficult to identify the interface between the nerve root and the ruptured disc and much less to mobilize and retract the nerve root without possibly causing nerve root injury. If the nerve root is challenging to detect, identifying the pedicle via palpation with a freer elevator can help locate the nerve root appropriately. After locating the lateral margin of the traversing nerve root and retracting the root and thecal sac medially, the ruptured fragment can be identified (Fig.  7a). The epidural space is comprehensively explored to confirm the type of LDH precisely and identify the location of the ruptured disc. Using straight or angled pituitary forceps, discectomy can be performed under endoscopic guidance (Fig. 7b, c). The goal

a

b

c

d

Fig. 7  Serial sequence endoscopic images of the discectomy in lumbar disc herniation. Identification of the ruptured fragment (black arrow) (a). Removal of the ruptured fragment (b, c). Confirmation of complete decompression (d)

Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis

of discectomy is to identify partially loose intradiscal fragments that could cause recurrent disc herniation, not to remove too many disc materials. After discectomy is completed, forceful intradiscal irrigation of the disc space helps to flush hidden intradiscal fragments and to facilitate their removal. The surgeon should then perform a final inspection of the epidural space after adequate discectomy to search for residual fragments. The traversing nerve root and the thecal sac can be identified based on good pulsation, which is the end point of decompression (Fig. 7d).

3 Postoperative Consideration 3.1 Dural Tear If a dural tear occurs during surgery, the dural defect must be primarily closed. Small-sized dural tear can be closed with a fibrin collagen patch (TachoComb) and bed rest for 5–7  days. The lack of significant dead space in UBE promotes a better tamponade effect and reduces the risk of dural–cutaneous fistula.

3.2 Postoperative Hematoma Bleeding from the bone edges is controlled with bone wax. Bleeding from the epidural vein can be coagulated using an RF probe. Hemostatic agents, such as Gelfoam, and soluble hemostatic gauze (WoundClot) are effective for controlling concealed epidural bleeding. To prevent postoperative epidural hematoma, the Jackson–Pratt drain (100 cc) should be placed for 1–2 days. If patients develop neurological symptoms due to hematoma, a hematoma can be removed via UBE using previous portals.

3.3 Fluid-Induced Complications The fluid-related complications include headache, neck stiffness, and seizure. Therefore, as

139

UBE is a fluid-medium surgery, caution should be taken, and fluid output must be monitored. Moreover, fluid-induced complications can be prevented via a semi-tubular retractor (Fig.  2a, b).

4 Case Illustration 4.1 Case 1: Lumbar Spinal Stenosis A 67-year-old man exhibited neurologic claudication caused by LSS at the L4–L5 level for 9  months. He was managed conservatively for 3  months; however, his symptoms aggravated. Preoperative magnetic resonance imaging (MRI) revealed LSS at the L4–L5 level (Fig. 8a–c). The thecal sac was compressed by the bilateral hypertrophied LF at the L4–L5 level. Unilateral laminectomy for bilateral decompression via UBE at the L4–L5 level was performed from the left side. Postoperative MRI revealed adequate decompression of the thecal sac at the L4–L5 level (Fig.  8d–f). Thereafter, the patient’s symptoms improved significantly.

4.2 Case 2: Lumbar Disc Herniation A 42-year-old female presented with left-side buttock pain, lower extremity paresthesia, and weakness for 2 months. LDH at the L4–L5 level was found on preoperative MRI, and a caudally migrating herniated disc fragment was discovered at the left side of the spinal canal in the sagittal/axial view (Fig.  9a–c). From the left side, UBE was used to perform discectomy at the L4– L5 level. The ruptured disc was removed, and the nerve root was decompressed thoroughly. Postoperative MRI confirmed this result after surgery (Fig.  9d–f). The patient’s pain significantly decreased after surgery. Furthermore, the physical strength of his lower extremities normalized at 1 month follow-up.

S.-K. Son and M. K. Park

140

a

b

c

d

e

f

Fig. 8  Images of a 67-year-old man with lumbar spinal stenosis at L4–L5 level. Preoperative MR images show lumbar spinal stenosis with bilateral hypertrophied LF at L4–L5 level (sagittal: a, axial: b, c). Postoperative axial T2-weighted MRI show enough decompression with minimal facet violation (sagittal: d, axial: e, f)

a

b

c

d

e

f

Fig. 9  Case of a 42-year-old female with lumbar disc herniation at L4–L5 level. Preoperative MR images show downward migrated lumbar disc herniation at L4–L5 level (sagittal: a, axial: b, c). Postoperative axial T2-weighted MRI show adequate decompression and no residual disc fragment (sagittal: d, axial: e, f)

Unilateral Biportal Endoscopy for Lumbar Disc Herniation and Stenosis

5 Summary Overall, UBE decompression may result in similar clinical outcomes with the potential for less morbidity and greater functional improvement than open procedures. UBE decompression is associated with a lower morbidity rate and better functional improvement compared with conventional surgery. Nevertheless, long-term, prospective, randomized clinical trials must be performed to compare the safety and efficacy of UBE decompression.

References 1. Mobbs RJ, Li J, Sivabalan P, Raley D, Rao PJ.  Outcomes after decompressive laminectomy for lumbar spinal stenosis: comparison between minimally invasive unilateral laminectomy for bilateral decompression and open laminectomy: clinical article. J Neurosurg Spine. 2014;21(2):179–86. 2. Carragee EJ, Han MY, Suen PW, Kim D.  Clinical outcomes after lumbar discectomy for sciatica: the effects of fragment type and anular competence. J Bone Joint Surg Am. 2003;85(1):102–8. 3. Wu CY, Jou IM, Yang WS, Yang CC, Chao LY, Huang YH.  Significance of the mass-compression effect of postlaminectomy/laminotomy fibrosis on histological changes on the dura mater and nerve root of the cauda equina: an experimental study in rats. J Orthop Sci. 2014;19(5):798–808. 4. Dvorak J, Gauchat MH, Valach L.  The outcome of surgery for lumbar disc herniation. I.  A 4-17 years’ follow-up with emphasis on somatic aspects. Spine (Phila Pa 1976). 1988;13(12):1418–22. 5. Heo DH, Quillo-Olvera J, Park CK.  Can percutaneous biportal endoscopic surgery achieve enough canal decompression for degenerative lumbar stenosis? Prospective case-control study. World Neurosurg. 2018;120:e684–9.

141

6. Hong YH, Kim SK, Suh DW, Lee SC. Novel instruments for percutaneous biportal endoscopic spine surgery for full decompression and dural management: a comparative analysis. Brain Sci. 2020;10(8):516. 7. Kim JE, Choi DJ, Park EJJ, Lee HJ, Hwang JH, Kim MC, et al. Biportal endoscopic spinal surgery for lumbar spinal stenosis. Asian Spine J. 2019;13(2):334–42. 8. Heo DH, Lee N, Park CW, Kim HS, Chung HJ.  Endoscopic unilateral laminotomy with bilateral discectomy using biportal endoscopic approach: technical report and preliminary clinical results. ­ World Neurosurg. 2020;137:31–7. 9. Hwa Eum J, Hwa Heo D, Son SK, Park CK.  Percutaneous biportal endoscopic decompression for lumbar spinal stenosis: a technical note and preliminary clinical results. J Neurosurg Spine. 2016;24(4):602–7. 10. Park SM, Kim GU, Kim HJ, Choi JH, Chang BS, Lee CK, et al. Is the use of a unilateral biportal endoscopic approach associated with rapid recovery after lumbar decompressive laminectomy? A preliminary analysis of a prospective randomized controlled trial. World Neurosurg. 2019;128:e709–18. 11. Pranata R, Lim MA, Vania R, July J. Biportal endoscopic spinal surgery versus microscopic decompression for lumbar spinal stenosis: a systematic review and meta-analysis. World Neurosurg. 2020;138:e450–8. 12. Park MK, Park SA, Son SK, Park WW, Choi SH. Clinical and radiological outcomes of unilateral biportal endoscopic lumbar interbody fusion (ULIF) compared with conventional posterior lumbar interbody fusion (PLIF): 1-year follow-up. Neurosurg Rev. 2019;42(3):753–61. 13. Park MK, Son SK, Park WW, Choi SH, Jung DY, Kim DH.  Unilateral biportal endoscopy for decompression of extraforaminal stenosis at the lumbosacral junction: surgical techniques and clinical outcomes. Neurospine. 2021;18(4):871–9. 14. Choi KC, Shim HK, Hwang JS, Shin SH, Lee DC, Jung HH, et al. Comparison of surgical invasiveness between microdiscectomy and 3 different endoscopic discectomy techniques for lumbar disc herniation. World Neurosurg. 2018;116:e750–8.

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine Nam Lee

1 Introduction

2 Indications

Microscopic spinal decompression for degenerative cervical and thoracic disease is the gold standard surgical treatment. Especially, posterior keyhole foraminotomy for cervical foraminal stenosis or herniated cervical disc has shown successful outcomes [1]. Posterior microscopic discectomy for thoracic disc herniation also has shown favorable outcomes [2, 3]. Recently, due to the development of endoscopic spinal surgery system, we can resolve these lesions with unilateral biportal endoscopy (UBE) technique. Park et  al. reported that endoscopic cervical foraminotomy using UBE surgery may be an alternative procedure for degenerative cervical foraminal disc protrusion [4]. This technique is similar to the conventional posterior surgical approach but has the advantages of less postoperative pain and faster recovery after surgery [5]. The purpose of this chapter is to describe the details of this UBE technique.

The indication of UBE surgery for degenerative cervical and thoracic lesion is very similar to conventional posterior decompression surgery using microscope. Indications for this technique include herniated cervical/thoracic disc (paramedian or foraminal or extra-foraminal type), foraminal stenosis of cervical spine, and ossification of ligamentum flavum (OLF) of thoracic spine. However, central herniated cervical/thoracic disc, cervical spondylotic myelopathy (CSM), and intrathecal disc herniation are contraindicated in this technique.

N. Lee (*) Department of Neurosurgery, Yonseicheok Hospital, Busan, Republic of Korea

3 Special UBE Instruments A zero-degree endoscope is mainly used in UBE surgery. Radiofrequency (Arthrocare®) probe is most commonly used to control intraoperative bleeding. The arthroscopic drill system with irrigation drain tube and high-speed electrical drill system is also used to remove the bony structure (Fig.  1a). The scope-retractor is also useful in preventing nerve root or thecal sac damage. The curved Kerrison punch is very useful to decompress the foraminal lesion. Most other conventional surgical instruments are available in this technique (Fig. 1b).

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_15

143

N. Lee

144

a

b

Fig. 1 (a) UBE special instruments. Zero-degree endoscope, Sheath, Radiofrequency probe, Arthroscopic drill, highspeed electrical drill (in order from the top). (b) Common conventional surgical instruments and the scope-retractor (black arrow)

a

b

Fig. 2 (a) Reverse Trendelenburg position with endotracheal general anesthesia for UBE cervical decompression. (b) The surgical field should be parallel to the floor with slight neck flexion

4 Anesthesia and Position Endotracheal general anesthesia is used in cervical and thoracic lesion. The author usually uses epidural anesthesia in lumbar lesion, but this method cannot be performed on the cervical and thoracic regions, general anesthesia is recommended. Prone position in reverse Trendelenburg with head fixation is suitable for cervical UBE decompression. It is important to make the s­ urgical field as parallel to the floor as possible for a comfortable posture for the surgeon (Fig. 2a, b). In the thoracic UBE decompression, the patient is always placed on a Wilson frame in the prone position. Usually, compression stockings are applied to prevent

thrombosis in the lower extremities during the surgery. The Foley catheter is also inserted to check the perioperative urine output.

5 Step-by-Step Technique (Schematic Illustration, More Than Four Figures) 5.1 Cervical UBE Decompression (Left-Side Approach, C6–7 Level) 1. Making two portals Under fluoroscopic imaging, setting the true A-P image is the first step for making portals.

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine

a

145

b 2cm

C6 C7 C6

C7

Fig. 3 (a) True A-P view. Pedicle of C6 is for scope portal (white circle) and pedicle of C7 is for instrument portal (yellow circle). (b) Lateral view. The distance between two portals is about 2 cm

C6

C7

Fig. 4  Intraoperative A-P view to confirm the V point of index level. The blunt hook indicates the V point of C6– C7, left side

Fig. 5  Illustration of UBE keyhole surgery. The keyhole was made at the V point of index level

Incision for endoscopic portal is placed on the pedicle of cranial vertebra (C6) and for instrument portal is placed on pedicle of caudal vertebra (C7). The usual distance between portals is about 2 cm (Fig. 3) and the size of each incision is about 1  cm. After skin incision, serial dilators are inserted sequentially. The first dilator should touch the V point—the junctional area of inferior border of lamina of C6 and superior border of lamina of C7 [6]. This V point is usually located in the medial border of the lateral mass of the index level (Fig. 4). The

author always makes the instrument portal first, and then followed by the endoscopic portal. The triangulation of two portals is a fundamental step of this technique. 2. Making initial working space Scraping the surface of bony structure around the V point using dilator is very important. When the purpose of the surgery is to remove the herniated cervical disc ­paramedian type, it is directed medially, and when it is to decompress the foraminal area, it is directed laterally (Fig. 5). This step is very important

N. Lee

146

a

b

MediaI

CraniaI

C6 Iamina

MediaI

CaudaI C6 Iamina

LateraI

C7 Iamina

LateraI

Fig. 6 (a) UBE endoscopic view. Black arrow indicates fine muscle and soft tissue. White arrow indicates V point of C6–C7. (b) After unveiling, a clear V point can be identified (white arrow)

a

b

C7 Iamina

Fig. 7 (a) A 2 mm Kerrison punch is applied to remove the lower lamina to increase the size of the keyhole. (b) The lateral margin of ligamentum flavum is identified (black arrow). The axillary portion of exiting nerve root is also identified (white arrow)

and critical to make initial working space, so the author recommends doing this under the guidance of fluoroscopic image. After sufficiently scrapping the surface of the bony structure, the 0° endoscope is inserted and the irrigation pump is started (usually 30 mmHg pressure). The field of view and space is gradually occupied by removing the fine muscle or soft tissues covering the V point using the RF device (Fig. 6a). RF coagulation mode as well as ablation mode are safe at this stage. Proper usage of the ablation mode is effective in reducing the operation time. This step is complete when the irrigation saline flows well towards the instrument portal and the V point is clearly visible (Fig. 6b).

3. Removal of bony structures (keyhole) and flavectomy The author usually starts the drilling from cranial bony part (C6) of V point due to right-­ handed surgeon. After that, the removal of caudal bony part (C7) of V point is undergone using drill or Kerrison punch (Fig.  7a). A 2  mm Kerrison punch is recommendable to avoid spinal cord or root injury. In this way, you can gradually increase the size of the keyhole. Then, the lateral margin of ligamentum flavum (LF) is identified. Since the area covered by the LF is smaller in the cervical spine than lumbar spine, the dura mater and nerve root are easily exposed (Fig. 7b). 4. Root decompression and discectomy

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine

a

ThecaI sac

147

b

C7 root

C7 root

C7 pedicIe

Fig. 8 (a) The compressed C7 nerve root is identified. More foraminal decompression should be done along the black arrow direction. (b) The dotted circle indicates pedicle of C7 and black arrow indicates axillar

a

b

Fig. 9 (a) The decompressed C7 nerve root is identified. Dotted white line indicates superior margin of nerve root and dotted black line indicates inferior margin of it. (b) A

The axillary portion of the exiting nerve root can be identified at the point where the LF ends laterally. And then, you can remove the bony structure causing the foraminal stenosis gradually along the running direction of the nerve root laterally (Fig. 8a). Even at this time, it is recommended to use only 2  mm Kerrison punch or foraminal punch to avoid nerve damage. The superior-medial margin of C7 pedicle will be detected in the inferior-­ lateral direction of the axilla (Fig.  8b). Confirming the exact position of the pedicle is very important in the orientation of surgery. To achieve sufficient foraminal decompression, the hypertrophied bony structure of

long-blunt hook can be entered into extra-foraminal area without resistance

intervertebral foramen must be removed as wide as the nerve root. In other words, both the superior and inferior margin of exiting nerve root should be identified without the retraction by hook or retractor (Fig.  9a). In addition, more than half of the lateral mass should be decompressed laterally. If the hook enters the intervertebral foramen effortlessly, it is considered that sufficient decompression is accomplished laterally (Fig. 9b). To expose the intervertebral disc to herniated cervical disc, you should retract the dura mater superior-medially from the axillary portion with a gentle touch. In this case, if the pressure of the dura mater is high and cannot

N. Lee

148

a

b

PartiaI pedicuIectomy

Fig. 10 (a) After partial pediculectomy, instrument can reach the ventral portion of thecal sac. (b) Using the hook and pituitary forceps, the herniated disc particles (black arrow) can be removed

a

b

C7 pedicIe

Fig. 11 (a) The inferior margin of pedicle of superior vertebra (black arrow) can be identified after gentle retraction of nerve root inferiorly. (b) The superior margin of pedicle of inferior vertebra is also shown (white arrow)

be retracted, partial pediculectomy can be applied. The partial pediculectomy provides additional space so that an instrument including pituitary forceps can be used easily to remove the herniated disc particle (Fig.  10a, b). 5. Finish the surgery and wound closure In the case of foraminal stenosis, you should identify the exposure from inferior margin of cranial pedicle (C6) to superior margin of caudal pedicle (C7) (Fig.  11a, b). And, in the case of HCD, the surgery can be finished when it is confirmed that there are no remnant disc particles left under the dura mater (Fig.  12a, b). After sufficient decompression, a drain catheter is always inserted

through the instrument portal and skin closure is done using absorbable suture material.

5.2 Thoracic UBE Decompression (Left-Side Approach, HTD T12/ L1) 1. Making two portals True A-P image under fluoroscopy is a cornerstone to start to make the portals. At the index level, the upper (T12) and lower (L1) pedicles are the skin incision points. As in cervical UBE surgery, the upper incision is used as an endoscopic portal, and the lower incision is used as an instrument portal. The two

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine

a

149

b

Fig. 12 (a) The long-blunt hook can detect the herniated disc particles in the para-central region. (b) The ventral area of nerve root and thecal sac can be identified

portals should meet each other on the laminar there may be severe adhesions between LF bone with triangulation. and dura mater. 2. Making initial working space 4. Thecal sac decompression and discectomy After sufficient scrapping using dilators on To achieve complete decompression, all the surface of the lamina, a 0° endoscope is ligamentum flavum from the ipsilateral to the inserted through the scopic portal. The irrigacontralateral side must be removed and both tion pump connected to the endoscope sheath lateral borders of the thecal sac should be is started and set to a pressure of about identified (Fig.  13a). The thecal sac can be 30–35 mmHg during the procedure. When the gently retracted medially using a scope retracsurface of the lamina is well identified and the tor or root retractor to identify the para-central soft tissue and muscle are clearly controlled area of the annulus and to remove the herniby RF device, the initial working space is ated disc material (Fig. 13b). Additional disachieved. cectomy was performed to remove the 3. Laminotomy and flavectomy remnant particles of disc protrusion or extruBoth arthroscopic drill system and high-­ sion cases using upward curved pituitary forspeed electrical drill system are useful to drill ceps or Kerrison punch (Fig.  14a). Even out the lamina. The author recommends using during the discectomy, the surgeon should a 2  mm Kerrison punch to remove the inner always check if the thecal sac is retracted cortex layer of lamina rather than drill system excessively medially or is under an iatrogenic because the vibration or heat of electrical drill damage. system can cause micro-trauma to the spinal 5. Finish the surgery and wound closure cord under thecal sac. The bony structure of When there is no ligamentum flavum the base of spinous process and contralateral remaining in the surgical field, bilateral borsublaminar area should be removed to reach ders of the thecal sac are clearly identified and the contralateral side. After finishing the bone the pulsation of spinal cord is confirmed, the work, the ligamentum flavum can be detached operation can be finished. In the case of HTD, from the thecal sac using double-ended retracif there are no herniated disc particles left and tors and removed by Kerrison punch or pituthe dura mater mobilizes well, it can be finitary forceps. In the case of ossification of ished. A drain is always inserted through the ligamentum flavum (OLF), the surgeon needs instrument portal. The location of the drain to be careful with meticulous touch because should not compress the spinal cord, so it is

N. Lee

150

a

b Contra-IateraI SAP

CraniaI

CaudaI

Fig. 13 (a) After flavectomy, lateral border of thecal sac is identified and adhesion tissue is also confirmed (black arrow). (b) The herniated disc particle is identified (black

a

arrow, contralateral side), the thecal sac is retracted medially with retractor (white arrow)

b

ThecaI sac

Fig. 14 (a) Additional discectomy is performed. The scope-retractor is useful to retract the thecal sac gently (black arrow). (b) The final view. Fully decompressed thecal sac is identified and a drain is identified (white arrow)

better to place little away from dura mater (Fig. 14b).

6 Perioperative Consideration and Case Illustration (If Applicable) The para-spinal muscles around the cervical spine are made up of several muscles. Each muscle has its own fascia, so if the surgeon does not sufficiently penetrate the fascia using a skin incision blade, it will be difficult to insert the dilator. Unlike the lumbar spine, in the cervical-thoracic region, the spinal cord runs in the spinal canal, not the spinal roots, so it is dangerous to angle the

dilators medially toward the spinal canal. In addition, if the cervical region is close to the brain, the surgeon needs to be more careful about the water pressure control. The proper pressure of water irrigation pump is about 25–30 mmHg. If the outflow of irrigation saline is not continuous, the pressure in the working space will increase, which may affect the intracranial pressure and cause seizure or epidural hematoma [7, 8]. Inadequate irrigation saline drainage seeps into the para-spinal muscles, increasing intra-muscle pressure, which in turn causes severe edema in the surgical site, and causes a vicious cycle in which irrigation saline drainage worsens as the instrument portal becomes narrower. Therefore, the author recommends the use of a sheath on the instrument por-

151

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine

tal. Keeping the semi-circular sheath for the instrument portal is very useful to maintain the stable continuous irrigation saline outflow.

side radiating pain and tingling sensation. The preoperative MRI images showed cervical foraminal stenosis C6–7 on left side and the C7 root was compressed significantly (Fig.  15a, b). The author underwent UBE foraminal decompression surgery with left-­ side approach. After decompression, the postoperative MRI showed well decompressed C7 nerve root at index level (POD 1  day) (Fig. 16a, b). The VAS score was significantly

6.1 Cervical Case Presentation 1. Foraminal stenosis case Sixty-four-years-old male patient complained of severe posterior neck pain and left-­ a

b C6/7

C6

Fig. 15  Preoperative MRI images. (a) Sagittal T2WI shows foraminal stenosis at C6/7. (b) Axial T2WI shows severe stenosis at foraminal area on left side

a

b

C6/7

C6

Fig. 16  Postoperative MRI images. (a) Sagittal T2WI shows well-­decompressed foraminal area at C6/7 (arrowheads indicate a drain line). (b) Axial T2WI shows decompressed foraminal area and there is no hematoma or muscle swelling

N. Lee

152

a

b

C7/T1

c

C7/T1

d

C8 root

Fig. 17 (a) Preoperative MRI image shows foraminal HCD at C7/T1 on left side. (b) postoperative MRI image shows complete removal of the lesion. (c) The C8 root is compressed by HCD. (d) The ruptured disc particle is identified under the root

decreased from 8 to 2 immediately and the patient was discharged 3 days after surgery. 2. HCD foraminal case (illustration case) Fifty-four-years-old male patient complained of severe tingling sensation on C8 dermatome, left side. This patient was recommended for elbow joint surgery at another hospital. However, the lesion was a cervical disc herniation, not an elbow joint problem. The preoperative MRI images showed a prominent HCD at C7/T1, left side and the C8

root was compressed (Fig. 17a). The removal of HCD using UBE technique was done. After exposing the C8 nerve root by making a keyhole at the V point, the nerve decompression was completed by removing the ruptured disc particle (Fig. 17c, d). The postoperative MRI images showed that the disc herniation was completely eliminated (Fig. 17b). Immediately after surgery, the patient’s tingling sensation and numbness almost disappeared and was discharged 4 days after surgery (Fig. 18a–c).

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine

a

b

153

c

Fig. 18  Illustration of UBE keyhole discectomy surgery. (a) The nerve root was compressed by HCD. (b) The keyhole for removing the HCD was made. (c) After removal of ruptured disc particle

a

b T12

T12/L1

Fig. 19  Preoperative MRI images. (a) Sagittal T2WI shows spinal stenosis and cord signal change at T12/L1. (b) Axial T2WI shows right-side paramedian HTD (white arrow) and severe compressed spinal cord

6.2 Thoracic Case Presentation Fifty-eight-years-old male patient visited my OPD with cane ambulation and he complained gait disturbance, numbness on the right side and back pain. The preoperative MRI images showed right-side paramedian herniated thoracic disc at T12/L1 with spinal cord signal change (Fig. 19a, b). UBE decompression with ULBD (unilateral

laminotomy and bilateral decompression) and contralateral side discectomy was done. The postoperative MRI images showed the complete removal of the herniated disc particle and restoration of normal shape of thecal sac and the spinal cord (Fig. 20a, b). After surgery, the patient can walk without a cane and the numbness was improved significantly. The patient was very satisfied with the postoperative outcome.

N. Lee

154

a

b

T12

T12/L1

Fig. 20  Postoperative MRI images. (a) Sagittal T2WI shows well-­decompressed spinal canal. (b) Axial T2WI shows the removed state of HTD (white arrow) and complete decompression of spinal canal. The base of spinous process was removed to reach the contralateral side (arrowhead)

7 Summary The endoscopic spine surgery is expected to become mainstream of the treatment of degenerative spinal disease [9]. The author insists that UBE technique is considered sufficient to meet such expectations because the UBE technique can be applied not only to cervical region, thoracic region, and lumbar region but also to fusion surgery and far-out syndrome [5, 10, 11]. UBE surgery in the cervical and thoracic region can be more critical when surgical-related complications occur, so it should be applied after the surgical technique has been sufficiently learned. However, as the author experienced, after UBE surgery for cervical and thoracic region, the postoperative pain is less, the recovery period after surgery is short, and the clinical results are very good. The advantage of this technique also includes preservation of the spinal stability not sacrifice of facet joint. It is hoped that many surgeons will learn this effective and safe technique and apply it to many degenerative spinal diseases.

References 1. Çağlar YŞ, Bozkurt M, Kahilogullari G, Tuna H, Bakir A, Torun F, et  al. Keyhole approach for posterior cervical discectomy: experience on 84 patients. min-­ Minimally Invasive. Neurosurgery. 2007;50(01):7–11. 2. Regev GJ, Salame K, Behrbalk E, Keynan O, Lidar Z. Minimally invasive transforaminal, thoracic microscopic discectomy: technical report and preliminary results and complications. Spine J. 2012;12(7): 570–6. 3. Perez-Cruet MJ, Kim B-S, Sandhu F, Samartzis D, Fessler RG. Thoracic microendoscopic discectomy. J Neurosurg Spine. 2004;1(1):58–63. 4. Park JH, Jun SG, Jung JT, Lee SJ. Posterior percutaneous endoscopic cervical foraminotomy and diskectomy with unilateral biportal endoscopy. Orthopedics. 2017;40(5):e779–83. 5. Heo DH, Park CK.  Clinical results of percutaneous biportal endoscopic lumbar interbody fusion with application of enhanced recovery after surgery. Neurosurg Focus. 2019;46(4):E18. 6. Xi Z, Lu Y, Xie L.  Endoscopic posterior cervical foraminotomy via a single stab incision for ­contiguous two-level cervical radiculopathy. Acta Neurochir. 2020;162(3):685–9. 7. Choi G, Kang H-Y, Modi HN, Prada N, Nicolau RJ, Joh JY, et al. Risk of developing seizure after percu-

Unilateral Biportal Endoscopic Surgery (UBE) for Cervical and Thoracic Spine taneous endoscopic lumbar discectomy. Clin Spine Surg. 2011;24(2):83–92. 8. Sairyo K, Matsuura T, Higashino K, Sakai T, Takata Y, Goda Y, et al. Surgery related complications in percutaneous endoscopic lumbar discectomy under local anesthesia. J Med Investig. 2014;61(3–4):264–9. 9. Ahn Y. Current techniques of endoscopic decompression in spine surgery. Ann Transl Med. 2019;7(Suppl 5):S169.

155

10. Kim JY, Heo DH. Contralateral sublaminar approach for decompression of the combined lateral recess, foraminal, and extraforaminal lesions using biportal endoscopy: a technical report. Acta Neurochir. 2021;163(10):2783–7. 11. Lee N, Heo DH, Park CK.  Biportal endoscopic approach (biportal endoscopic lumbar discectomy), Advanced techniques of endoscopic lumbar spine surgery. Singapore: Springer; 2020. p. 123–36.

Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion Hyeun Sung Kim

1 Introduction Endoscopic spine surgery is an increasingly popular subspecialty of minimally invasive spine surgery. Having an optical lens at the distal end of the endoscope, the operating surgeon can visualize target structures under illumination and magnification. Constant saline irrigation helps to maintain clarity of field free of bony and soft tissue debris and blood. As it is docked directly at the target, there is minimal soft tissue trauma. While early endoscopic practice largely focuses on the performance of discectomy, the benefit zone increases significantly if lumbar interbody fusion can be performed under uniportal full endoscopic technique [1]. There is a steep learning curve for spinal endoscopic surgeon to be proficient in endoscopic lumbar interbody fusion [2]. There are two types of pathways in which the surgeon can partake to proceed with endplate preparation in the interbody disc space. The first pathway is a natural safe anatomical working zone in Kambin’s triangle adjacent to the exiting nerve root (uniportal full endoscopic, facet preserving trans-Kambin transfoH. S. Kim (*) Nanoori Hospital, Seoul, Republic of Korea

raminal lumbar interbody fusion). The second pathway is through the interlaminar window with facet resection to create the working space required adjacent to the traversing nerve root, namely, (uniportal full endoscopic, facet sacrificing posterolateral transforaminal lumbar interbody fusion) [3]. Our focus in this chapter is on uniportal full endoscopic, facet sacrificing posterolateral transforaminal lumbar interbody fusion.

2 Indications Both uniportal full endoscopic transforaminal lumbar interbody fusion techniques have similar indications to open and minimally invasive transforaminal lumbar interbody fusion. Common indications described in the literature are spinal instability with degenerative disc disease, unstable spondylolisthesis, spinal stenosis with both mechanical back and leg pain due to instability, foraminal stenosis, recurrent disc herniations who had undergone failed discectomy and facet joint instability [3]. In addition, patients who are unfit for general anesthesia can consider uniportal full endoscopic, facet preserving trans-­ Kambin transforaminal lumbar interbody fusion [4].

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_16

157

H. S. Kim

158

3 Step-by-Step Technique 3.1 Uniportal Full Endoscopic, Facet Sacrificing Posterolateral Transforaminal Lumbar Interbody Fusion The general principle steps of uniportal full endoscopic, facet sacrificing posterolateral transforaminal lumbar interbody fusion are similar to minimally invasive transforaminal lumbar ­interbody fusion using tubular retractor. However, there are some significant technical differences due to higher magnification and more mobility of endoscope with limited size of equipment by the dimension of working channel and there is a steep learning curve in this technique [5–8]. In terms of handling of the inferior articular process (IAP), the technique can be performed from an outside-in approach or inside-out approach. There is a statistically significant difference in these two ways of approaching IAP with the outside-­ in approach faster than the inside-out approach [8]. We recommend the usage of a large inner diameter work channel stenosis endoscope to perform this fusion procedure.

3.1.1 Step 1: Docking of Uniportal Stenosis Dimension Endoscope on Pars Interarticularis We placed patient prone on a Wilson Frame with the spine in slight flexion under general anesthea

b

Fig. 1  The endoscopic docking points. (a) The endoscope is docked on the facet joint, yellow arrow is the Wu’s point which is close to the fluoroscopic image of the medial confluence of the medial edge of outline of inferior articular process (red line) and superior articular process (blue line) while white arrow is the Kim’s point which is

sia. The patient’s back will be flattened upon placement of rods before final locking to restore lordosis in the patient. The surgeon stands on the side and full facet resection and cage insertion are planned. We marked a 1.6 cm skin incision on the upper vertebral pedicle of the symptomatic side and at the level of facet resection which is seen on AP view (Fig.  1). A corresponding lateral view would show the working cannula is in line with the disc space. We performed serial dilation with guidewire, dilators, and finally retractor cannula. The working cannula would be docked on the medial part of the inferior border of IAP, directly on the pars interarticularis. The surgeon subsequently moved the endoscope to Wu’s point for inside-out approach or Kim’s point for the outsidein approach, respectively (Fig.  1). This docked position is checked on AP/Lateral fluoroscopy view to confirm correct position of endoscope. We recommend using a 10–15° viewing angle, 10 mm outer diameter, 5.1–6 mm working channel diameter, and 120–130 mm working length endoscope to perform this procedure. Endoscopic irrigation pressure is maintained at 25–40  mmHg in most parts of the endoscopic fusion procedure.

3.1.2 Step 2: Resection of Inferior Articular Process: Inside-Out Versus Outside-In Approach Using the radiofrequency ablator, soft tissue dissection defines the pars interarticularis and releases the facet capsule. During the bony landc

close to the fluoroscopic image of the lateral confluence of the lateral edge of outline of inferior articular process (red line) and superior articular process (blue line). (b) Preoperative 3D reconstructed CT scan assisted in the planning of the docking region on Wu’s point (blue circle) and (c) Kim’s point (red circle)

Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion

mark exposure, we looked for the endoscopic landmark of spinolaminar junction and medial rounded edge of the facet joint, identified the midpoint of the bony arch formed from spinolaminar junction and most inferomedial aspect of the inferior articular facet which is described as Wu’s point [8]. Soft tissue dissection is extended laterally to expose the most superior and lateral edge of the inferior articular process articulating with superolateral edge of the superior articular process, described as Kim’s point [8]. Wu’s point is medial and relatively more caudal aspect of the facet while Kim’s point is on the lateral aspect and relatively more cephalad of the facet joint. Endoscopic drilling starting at Wu’s point towards Kim’s point is known as inside-out approach, while endoscopic drilling performed in the vice versa direction is known as outside-in approach. In the inside-out approach, IAP is resected from Wu’s point in an oblique caudal to cephalad and medial to lateral direction towards Kim’s point. One would encounter outer cortical bone, inner cancellous bone, and inner cortical

bone while doing endoscopic drilling. We drilled till a thin layer of inner cortex was left. Using the large working retractor tube, we performed controlled fracture of the IAP’s endoscopic drilling track. IAP is harvested as an autograft. The outside-­in approach involved endoscopic drilling in an oblique cephalad to caudal, lateral to medial approach from Kim’s point towards Wu’s point. We found that doing outside-in approach has the advantage of less bleeding when IAP fracture and less soft tissue dissection of the rotators muscle required, both of these factors led to a statistically significant quicker resection of IAP [8] (Figs. 2 and 3).

3.1.3 Step 3: Resection of Superior Articular Process Superior articular process (SAP) is exposed after IAP is resected. We palpate the medial edge of the base of SAP with endoscopic Penfield probe, we subsequently resect SAP from medial to lateral or lateral to medial direction using endoscopic drill (Fig. 2d–f). Alternatively, endoscopic

a

b

c

d

e

f

Fig. 2  Preoperative 3D reconstructed CT scan of uniportal full endoscopic, posterolateral transforaminal lumbar interbody fusion handling of superior and inferior articular process of right L4/5. (a) Soft tissue dissection of multifidus muscle which draped over the isthmus and facet joint. Exposure of the facet joint shaded in red. (b, c) Endoscopic drilling point of inferior articular process (IAP). (b) Exposure of Wu’s point (blue circle) of IAP. (c)

159

Endoscopic drilling done layer by layer to the inner layer of cortex of isthmus, thinning the isthmus to inner cortex towards Kim’s point of IAP (red circle). (d–f) Endoscopic drilling procedures of superior articular process (SAP). (d) Endoscopic drilling on the inferior medial edge of superior articular process to inferior midpoint of superior articular process above the pedicle (e) and subsequently to inferior lateral edge of superior articular process (f)

H. S. Kim

160

a

b

Fig. 3  Intraoperative endoscopic picture of right L4/5 uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion demonstrating resection of inferior articular process using inside-out approach. (a) Exposure of Wu’s point (yellow dash circle), the midpoint of the bony arch formed from spinolaminar junction and most superomedial aspect of inferior articular facet. (b)

a

b

c

Endoscopic drilling of the isthmus. (c) Complete resection of isthmus of right L4/5 inferior articular process from Wu’s point to Kim’s point, the most superior and lateral edge of inferior articular process articulating with superolateral edge of superior articular process. Conversely, in the outside-in approach, drilling is carried out from Kim’s point to Wu’s point

c

Fig. 4  Intraoperative endoscopic picture of right L4/5 uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion demonstrating resection of superior articular process. (a) Removal of inferior articular

process (IAP) using working cannula to lift up the facet. (b) Exposure of the superior articular process (SAP). (c) Medial edge of SAP (yellow circle) and lateral edge of SAP (red circle)

Kerrison punch can be used to harvest SAP piecemeal as autograft (Fig. 4).

removed. We observed for pulsating decompressed neural elements.

3.1.4 Step 4: Flavecectomy and Decompression of Neural Elements After SAP resection, the lateral margin of ligamentum flavum is exposed. Endoscopic drilling of the lamina attachment of the cephalad and caudal margin of ligamentum flavum is subsequently performed till the edges of ligamentum flavum. If it is necessary for bilateral lateral recess stenosis cases, over-the-top decompression of contralateral side is performed. Once sufficient bony decompression is performed to edges of ligamentum flavum, ligamentum flavum (flava) are

3.1.5 Step 5: Intervertebral Disc Preparation and Cage Insertion We exposed the disc and performed hemostasis on the epidural vessels adjacent to disc space (Fig. 5). Under radiological and endoscopic guidance, intervertebral disc annulotomy is performed using endoscopic Penfield and radiofrequency ablator. A large size opens beveled working cannula of 13.7 mm outer diameter and 10.2  mm inner diameter is advanced and placed firmly on the disc. The open bevel is pointed away from the neural elements. We gently retract the traversing nerve root medially with

Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion

a

b

Fig. 5  Endoscopic pictures of uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion of right L4/5. (a) Disc exposure with working cannula rotated to protect traversing nerve root. (b) Denudation of

a

161

c

end plate cartilages from cephalad endplate and caudal endplate with endoscopic drill, blunt bent dissector, and pituitary forceps to remove disc and cartilage. (c) Completion of endplate preparation

b

Fig. 6  Final confirmation of cage insertion in the endoscopic view. (a) A 3D-printed titanium cage inserted with autograft packed in the cage. (b) Pulsating traversing nerve root seen adjacent to the cage

the working cannula. The endplate cartilage is denuded with endoscopic drill and endoscopic blunt bent probe till punctate bleeding of subchondral bone is seen, disc fragments are retrieved with endoscopic forceps. We performed an inspection of endplate to ensure satisfactory endplate preparation. After then, we advanced the working cannula ventrally into the dorsal third of the intervertebral disc space with the neural elements protected by working retractor and endoscope is withdrawn. The next portion of surgery is performed under fluoroscopic guidance. Autograft and allograft admixture is inserted into the intervertebral disc space. Trial of cage size is performed and subsequently an appropriate sized

cage packed with autograft and allograft admixture is inserted into the working cannula. If the cage is larger than the working cannula of the endoscope, we insert a dilator and thread through a Harrison cage glider into the appropriate position under fluoroscopic guidance [5] (Fig. 6). A final cage insertion is performed through the Harrison cage glider under endoscopic guidance. The endoscope is inserted to inspect the cage position and status of neural decompression. Drain is inserted through the endoscope and anchored with suture. Drain would be typically removed on postoperative day 1. We flatten the Wilson frame after cage insertion and insert percutaneous pedicle screws and

H. S. Kim

162

a

b

c

d

e

f

Fig. 7  Intraoperative fluoroscopy showing insertion of interbody cage in L5/S1 posterolateral lumbar interbody fusion. (a) Working cannula retracted traversing nerve root. (b) Packing of bone graft in the interbody space. (c) Harrison cage glider inserted to protect traversing nerve

root. (d) Cage insertion through the Harrison cage glider which subsequently removed ventral third of cage inserted in the interbody space. (e, f) Cage inserted in the interbody space

rods under fluoroscopic guidance in standard fashions with compression and final tightening of the set screws and closed the wound in layers (Fig. 7).

ing X-ray is done to evaluate the cage and screws positioning. Postoperative MRI within a week is an optional practice in some countries where MRI cost and availability is acceptable to the patient population. Gentle ambulation and non-­ weight-­bearing exercises are encouraged to be performed in the first 2 weeks. Strenuous activities should be carried out after 3–6 months. We generally avoid flexion activities unless necessary to avoid stress on implants and screws till fusion has taken place. Fusion is tracked by follow-­up X-ray with or without CT scan. Majority of our patients fused within 1 year [4] (Figs. 8, 9, and 10).

4 Postoperative Consideration and Case Illustration For both types of endoscopic fusion, they are ambulatory on the same day if not the next morning. If the drain is inserted, it would be removed the next morning. Jewett brace is offered as an option for comfort for the patient, but it is not absolutely necessary. Postoperative day 1 stand-

Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion

163

a

b

ai

ci

c

d

bi

di

Fig. 8  Preoperative and postoperative CT scan and MRI for uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion of right L4/5. (a) Preoperative sagittal MRI midline cut of L4/5 showing spinal stenosis with grade 1 spondylolisthesis of L4/5. (b) Preoperative coronal CT cut showing lateral listhesis of L45 with vacuum sign on the disc of L4/5. (c) Preoperative axial MRI of L4/5 showing spinal stenosis. (d) Preoperative sagittal

cut CT scan showing grade 1 spondylolisthesis with pars defect. (ai) Postoperative MRI sagittal midline cut showing decompression of L4/5. (bi) Postoperative coronal CT cut showing correction of lateral listhesis of L45 with cage inserted in the disc of L4/5. (ci) postoperative axial MRI of L4/5 showing decompressed L4/5 spinal canal. (di) Postoperative sagittal cut CT scan showing reduction of spondylolisthesis after cage inserted

a

b

c

d

e

f

g

h

i

j

k

l

Fig. 9  A 56-year-old female patient who underwent L5-S1 uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion. (a–d) Preoperative X-ray and CT images. (e–h) Immediate postoperative X-ray and CT images. (i–l) 2 year follow-up X-ray and CT images

H. S. Kim

164

a

b

c

d

e

f

Fig. 10  A 66-year-old female patient who underwent revision left L3/4 and right L5/S1 uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion for adjacent segment degeneration of previous L4/5 fusion. (a–c) Preoperative X-ray and whole spine images. (d–f) 1 year follow-up X-ray and whole spine images

5 Summary Uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion and uniportal full endoscopic trans-Kambin transforaminal lumbar interbody fusion are safe and minimally invasive procedure under experienced hands. Careful selection of patients and familiarity with the steps in endoscopic fusion are important to improve safety, efficacy, and efficiency of the operation. When well-executed, it provides m ­ inimally invasive benefits with similar long-term outcomes as an open spinal fusion procedure.

References 1. Hasan S, Hartl R, Hofstetter CP. The benefit zone of full-endoscopic spine surgery. J Spine Surg (Hong Kong). 2019;5(Suppl 1):S41–56.

2. Wu PH, Kim HS, Choi DJ, Gamaliel Y-HT. Overview of tips in overcoming learning curve in uniportal and biportal endoscopic spine surgery. J Minim Invasive Spine Surg Tech. 2021;6(Suppl 1):S84–96. 3. Kim HS, Wu PH, Sairyo K, Jang IT. A narrative review of uniportal endoscopic lumbar interbody fusion: comparison of uniportal facet-preserving trans-­ Kambin endoscopic fusion and uniportal facet-sacrificing posterolateral transforaminal lumbar interbody fusion. Int J Spine Surg. 2021;15(Suppl 3):S72–83. 4. Shen J.  Fully endoscopic lumbar laminectomy and transforaminal lumbar interbody fusion under local anesthesia with conscious sedation: a case series. Biomed Res Int. 2019;127:e745–50. 5. Kim H-S, Wu PH, Lee YJ, Kim DH, Jang IT. Technical considerations of uniportal endoscopic posterolateral lumbar interbody fusion: a review of its early clinical results in application in adult degenerative scoliosis. World Neurosurg. 2020; https://doi.org/10.1016/j. wneu.2020.05.239. 6. Wu PH, Kim HS, Lee YJ, Kim DH, Lee JH, Jeon JB, et  al. Uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion with endoscopic disc drilling preparation technique for symptomatic foraminal stenosis secondary to severe collapsed disc

Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion space: a clinical and computer tomographic study with technical note. Brain Sci. 2020;10(6):373. 7. Kim HS, Wu PH, Jang I-T.  Technical note on Uniportal full endoscopic posterolateral approach transforaminal lumbar interbody fusion with reduction for grade 2 spondylolisthesis. Interdiscipl Neurosurg. 2020;21:100712.

165

8. Kim H-S, Wu P-H, An J-W, Lee Y-J, Lee J-H, Kim M-H, et  al. Evaluation of two methods (inside-out/ outside-in) inferior articular process resection for uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion: technical note. Brain Sci. 2021;11(9):1169.

Biportal Endoscopic Lumbar Interbody Fusion Dong Hwa Heo, Don Young Park, and Young Ho Hong

1 Introduction Recently, the indications of endoscopic spine surgery have been vigorously expanded. Endoscopic lumbar interbody fusion surgeries have been attempted for lumbar degenerative disease and instability. Among them, biportal endoscopic lumbar approach also can achieve lumbar interbody fusion surgery. Biportal endoscopic lumbar interbody fusion surgeries may have the advantages of minimally invasive lumbar fusion surgeries as well as endoscopic lumbar approaches [1–3]. The technique of biportal endoscopic lumbar interbody fusion surgery can perform complete fusion procedures as well as neural decompression like conventional surgery or microscopic surgery [4, 5]. Minimal invasiveness and minimizing normal structures were other benefits of biportal endoscopic lumbar interbody fusion [5, 6]. Since the technique of biportal endoscopic lumbar fusion surgery usually followed the method of ipsilateral transforaminal lumbar

D. H. Heo · Y. H. Hong (*) Neurosurgery, Endoscopic Spine Surgery Center, Champodonamu spine hospital, Seoul, Republic of Korea D. Y. Park Orthopedics, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA

interbody fusion (TLIF) using tubular retractor, anatomical orientation is familiar to spine surgeons. We introduce the surgical technique and procedures of biportal endoscopic TLIF including its modified techniques.

2 Indications The indication of biportal endoscopic TLIF is the same as minimally invasive TLIF using tubular retractor systems [1, 7, 8]. The indications of biportal endoscopic TLIF were degenerative spondylolisthesis, Isthmic spondylolisthesis, central or lateral recess stenosis with instability, foraminal stenosis, and recurrent disc herniation in lumbar lesion. In contrast, contraindications of this technique were tumorous condition, infection, and deformity such as scoliosis and kyphosis [3, 6, 8, 9].

3 Step-by-Step Technique There were two approaches of endoscopic TLIF (Fig. 1). One is trans-Kambin approach (Fig. 1a) and the other is posterolateral approach (Fig. 1b) [1, 5, 8]. Biportal endoscopic TLIF used the corridor of posterolateral approach. The surgical technique of biportal endoscopic TLIF using posterolateral approach is similar to minimally invasive TLIF using tubular retractor systems [2, 5,

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_17

167

D. H. Heo et al.

168

a

b

Fig. 1  Two approaches of endoscopic TLIF: trans-Kambin approach (a) and posterolateral approach (b). Trans-­Kambin approach was similar to transforaminal endoscopic discectomy. In contrast, posterolateral approach was similar to conventional or minimally invasive TLIF

10]. Comparing endoscopic TLIF using trans-­ Kambin approach, this posterolateral TLIF approach (Fig.  1b) performed wide bone work including ipsilateral laminectomy and facetectomy [5, 9].

3.1 Skin Incision and Making Two Portals Two portals were made over the ipsilateral pedicles [3, 5, 11]. For the right-handed surgeon, the portal for right hand was usually a working portal [6]. In left-sided approach of L45 interbody fusion, an endoscopic portal was made over the cranial L4 pedicle and a working portal was made over the L5 pedicle. These two skin incisions were used for ipsilateral percutaneous pedicle screw insertion (Fig. 2a). There were other incision points of making; an endoscopic portal was made over the cranial lamina, and a working portal was made around the ipsilateral caudal pedicle (Fig. 2b). The medial endoscopic portal was useful for good visualization of upper and lower endplate during discectomy and endplate preparation. Small skin incision for an endoscopic portal was also used for an epidural drainage catheter. Two portals should be made under C-arm fluoro-

scopic monitoring. An endoscopic portal was used for endoscopy and its trocar by non-­ dominant hand, and a working portal was used for surgical instruments by dominant hand (Fig.  3) [5, 9]. Serial dilators were inserted to make the working portal. Finally, a working sheath was inserted (Fig. 3).

3.2 Bone Work with Nerve Root Decompression For the direct decompression of ipsilateral nerve root and contralateral nerve root, wide bone work is necessary. Usually, ipsilateral partial hemilaminectomy and ipsilateral facetectomy were done (Fig. 4a, b). Proximal and distal end of ligamentum flavum should be exposed after partial hemilaminectomy of cranial and caudal laminae. Ipsilateral facetectomy was done including removal of inferior and superior articular process. Sometimes, superior articular process was partially removed for protection of exiting nerve root during a cage insertion. After laminectomy and facetectomy, ligamentum flavum was removed. If patients have contralateral lateral recess stenosis, we removed ligamentum flavum bilaterally. Contralateral ligamentum flavum was

Biportal Endoscopic Lumbar Interbody Fusion

a

169

b

Fig. 2  Two skin incision points for two portals. Two skin stab wound were made at lateral border of pedicles (a). Another location of an endoscopic portal was over the cranial laminae (b)

3.3 Discectomy Endplate Preparation

Fig. 3  Overview of biportal endoscopic approach. A working sheath (arrow) was inserted at a working portal

removed via sublaminar approach. Central canal and bilateral traversing nerve roots can be decompressed (Fig. 4c).

After decompression of central canal and nerve roots, total discectomy was performed. Usual annulotomy and discectomy were done with pituitary forceps and shavers. Up-bite angled pituitary forceps was useful to do contralateral side discectomy. We can do complete endplate preparation under a clear magnified endoscopic view (Fig.  5a). An endoscopy can be inserted into intervertebral space. Endplate consisted of two layers including osseous endplate and cartilaginous endplate. For the prevention of cages subsidence, only cartilaginous endplate should be removed without injury of osseous endplate (Fig. 5b). In biportal endoscopic TLIF, only cartilaginous endplate can be separated and removed from osseous endplate under endoscopic view. Contralateral endplate preparation was done with angled curettes. Complete endplate preparation

D. H. Heo et al.

170

a

c

b

Fig. 4 (a) Intraoperative endoscopic view of ipsilateral laminotomy with removal of inferior articular process. (b) After removal of superior articular process, there were enough space for cage insertion. Also, ipsilateral travers-

a

ing nerve root was fully decompressed. (c) A contralateral traversing nerve root was completely decompressed after removal of contralateral ligamentum flavum

b

Fig. 5  Intraoperative endoscopic view of complete endplate preparation (a). There was no violation of osseous endplate (b)

was achieved under a clear magnified endoscopic view (Fig. 5) [4, 5, 9].

3.4 Cage Insertion • One cage insertion technique: Before cage insertion, we checked the distance of ­intervertebral space using serial size of cage trials or shavers (Fig.  6a). If there was disc space narrowing, we tried distraction of interbody space for indirect decompression of foramen and insertion of a large size cage. Serial insertion of cage trials can perform the

distraction of disc space. A cage was inserted after retraction dura and traversing nerve root under C-arm fluoroscopic monitoring (Fig. 6b). Obliquely inserted cage was rotated transversely using a cage impactor (Figs.  6c and 7) [3, 9]. • Two cages insertion technique: Two cages of posterior lumbar interbody fusion (PLIF) can be inserted unilaterally [5]. First PLIF cage should be inserted deeply over the midline (Figs. 8 and 9). And then, a second PLIF cage was inserted into interbody space. Finally, bone chips were inserted between two cages (Figs. 8 and 9) [5].

Biportal Endoscopic Lumbar Interbody Fusion

a

171

b

c

Fig. 6 (a) A cage trial was inserted for measuring of distance of interbody space. (b) A large-sized cage was inserted under dura retraction. (c) A cage was rotated transversely

a

b

Fig. 7  Illustration of a cage insertion (a) and rotation (b). (a) Initially, a cage was inserted obliquely into the interbody space. (b) Obliquely inserted cage was usually rotated transversely using a cage impactor

3.5 Percutaneous Pedicle Screw Insertion After putting in cages into interbody space, percutaneous pedicle screw fixation was performed under C-arm fluoroscopic monitoring. Two skin

incisions for two portals were used for ipsilateral percutaneous pedicle screws fixation. On the contralateral side, two skin incisions were additionally made for contralateral percutaneous pedicle screw fixation.

D. H. Heo et al.

172

a

b

c

Fig. 8  Schematic illustration of two PLIF cages insertion technique. First cage was inserted over the midline (a), and second cage was put in ipsilateral interbody space (b). Fusion material materials were packed into space between two PILF cages (c)

a

b

c

Fig. 9  Intraoperative endoscopic images of two cages insertion technique. First cage insertion (a), second cage insertion (b), and bone chips packing between two cages (c)

4 Postoperative Consideration

5 Case Illustration

A drainage catheter was maintained 2 days after biportal endoscopic TLIF.  We recommended wearing the orthosis such as corset or TLSO brace during 8 weeks after surgery.

Case 1. A 61-Year-old female patient presented with bilateral leg pain and neurological intermittent claudication. Preoperative X-ray and MRI revealed degenerative spondylolisthesis

Biportal Endoscopic Lumbar Interbody Fusion

173

a

b

c

e

f

g

d

h

Fig. 10  Preoperative X-ray (a, b) and MRI (c, d) images show degenerative spondylolisthesis with central stenosis of L4–5. We performed biportal endoscopic TLIF in L4–5 area. Postoperative X-ray (e, f) and MRI (g, h) reveal wellreduced spondylolisthesis and complete decompression of central canal at L4–5

and stenosis at L4–5 (Fig. 10a–d). This patient received biportal endoscopic TLIF using a large-sized cage. Postoperative MRI depicted well-decompressed central stenosis and reduction of spondylolisthesis of L4–5. Also, postoperative X-ray showed a large-size cage insertion and well-reduced spondylolisthesis of L4–5 (Fig. 10e–h). This patient’s symptoms were significantly improved after biportal endoscopic TLIF. Case 2. A 72-Year-old male patient complained of radiating pain in both legs and claudication.

Preoperative X-ray showed degenerative spondylolisthesis of L4–5 and preoperative MRI revealed stenosis of L4–5 (Fig. 11a–d). We did biportal endoscopic TLIF using two cages insertion technique. Postoperative MRI and X-ray depicted well-decompressed central stenosis and reduction of spondylolisthesis at L45. And two cages were inserted at L45 of interbody space (Fig. 11e–h). After surgery, radiating pain was resolved.

D. H. Heo et al.

174

a

b

c

d

e

f

g

h

Fig. 11  Preoperative X-ray (a, b) and MRI (c, d) images depict degenerative spondylolisthesis with central stenosis of L4–5. We performed biportal endoscopic TLIF in L4–5 area. Postoperative X-ray (e, f) and MRI (g, h) show wellreduced spondylolisthesis and complete decompression of central canal at L4–5

6 Summary This biportal endoscopic TLIF can achieve complete neural decompression through laminotomy and removal of ligamentum flavum. Endoscopic endplate preparation can prevent osseous endplate injury and subsidence of cage. Minimizing of traumatization of muscle injury is the advantage of biportal endoscopic TLIF. Moreover, enhanced early recovery after surgery and lower postoperative wound pain were other advantages of biportal endoscopic lumbar fusion surgeries. In spite of the advantages of biportal endoscopic TLIF, this surgical technique may have technical difficulties and need a learning curve. We strongly recommend that you should have a lot of experience in basic biportal endoscopic lumbar surgery including discectomy and decompression before starting this fusion surgery.

References 1. Heo DH, Lee DC, Kim HS, Park CK, Chung H.  Clinical results and complications of endoscopic lumbar interbody fusion for lumbar degenerative disease: a meta-analysis. World Neurosurg. 2021;145:396–404. 2. Heo DH, Park CK.  Clinical results of percutaneous biportal endoscopic lumbar interbody fusion with application of enhanced recovery after surgery. Neurosurg Focus. 2019;46(4):E18. 3. Park MK, Park SA, Son SK, Park WW, Choi SH. Clinical and radiological outcomes of unilateral biportal endoscopic lumbar interbody fusion (ULIF) compared with conventional posterior lumbar interbody fusion (PLIF): 1-year follow-up. Neurosurg Rev. 2019;42(3):753–61. 4. Heo DH, Son SK, Eum JH, Park CK.  Fully endoscopic lumbar interbody fusion using a percutaneous unilateral biportal endoscopic technique: technical note and preliminary clinical results. Neurosurg Focus. 2017;43(2):E8. 5. Heo DH, Hong YH, Lee DC, Chung HJ, Park CK. Technique of biportal endoscopic transforaminal

Biportal Endoscopic Lumbar Interbody Fusion lumbar interbody fusion. Neurospine. 2020;17(Suppl 1):S129–37. 6. Kang MS, You KH, Choi JY, Heo DH, Chung HJ, Park HJ.  Minimally invasive transforaminal lumbar interbody fusion using the biportal endoscopic techniques versus microscopic tubular technique. Spine J. 2021;21(12):2066–77. 7. Schwender JD, Holly LT, Rouben DP, Foley KT. Minimally invasive transforaminal lumbar interbody fusion (TLIF): technical feasibility and initial results. J Spinal Disord Tech. 2005;18(Suppl):S1–6. 8. Kang MS, Heo DH, Kim HB, Chung HT.  Biportal endoscopic technique for transforaminal lumbar interbody fusion: review of current research. Int J Spine Surg. 2021;15(Suppl 3):S84–92.

175 9. Heo DH, Eum JH, Jo JY, Chung H.  Modified far lateral endoscopic transforaminal lumbar interbody fusion using a biportal endoscopic approach: technical report and preliminary results. Acta Neurochir (Wien). 2021;163(4):1205–9. 10. Khan NR, Clark AJ, Lee SL, Venable GT, Rossi NB, Foley KT. Surgical outcomes for minimally invasive vs open transforaminal lumbar interbody fusion: an updated systematic review and meta-analysis. Neurosurgery. 2015;77(6):847–74; discussion 74. 11. Heo DH, Kim JY, Park JY, Kim JS, Kim HS, Roh J, et  al. Clinical experiences of 3-dimensional biportal endoscopic spine surgery for lumbar degenerative disease. Oper Neurosurg (Hagerstown). 2022;22(4):231–8.

Part III Minimally Invasive Spinal Procedure

Overview of Minimally Invasive Spine Surgery with the Tubular Retractor Jong Un Lee and Dae-Hyun Kim

1 Introduction The tubular retractors are considered as the remarkable technological development in spinal surgery from a minimally invasive point of view. Through fixed or expandable retractors, MISS gained popularity as the more conventional microsurgical techniques could be used similarly to open surgery. The most important principle of MISS is to avoid injury to the posterior paraspinal muscles that are responsible for maintaining the integrity of intervertebral discs, facet joints, and ligaments. Especially, the Multifidus muscle is located medially and its tendon is attached to the spinous process. Thus, it is most severely injured when using the midline approach. This leads to long-term muscle atrophy, which leads to disruption of spinal posture and its neutral position. Maintaining multifidus tendon attachment to the spinous process and integrity of dorsolumbar fascia would be accomplished by using paramedian approaches rather than the midline approaches. The tubular retractor system splits the muscle instead of cutting it, and the cylindrical retractor allows the surgical corridor to be opened via serial dilation using sequentially larger concentric tubes. This decreases the need for muscle J. U. Lee (*) · D.-H. Kim Department of Neurosurgery, Daegu Catholic University Medical Center, Daegu, Republic of Korea e-mail: [email protected]

stripping during exposure. Another principle of MISS using the tubular retractor is the use of a retractor holder mounted to the table instead of using a “self-retaining” mechanism. This would reduce the pressure on the tissues for holding the retractor in place. Stevens et al. reported that the maximum intermuscular pressure around a tubular retractor decreases by 50% within 3  s since the retractor holder had been attached [1]. Furthermore, a tubular retractor maximizes the surface contact area, which, in turn, minimizes the pressure per unit area. Through these principles, the retractor predisposes the muscle to lesser retraction pressures and makes it less vulnerable to disruption of its neurovascular supply.

2 Main Text The tubular retractor system was developed by Foley and Smith and consists of a series of concentric dilators and thin-walled (0.9 mm) tubular retractors of variable length. The appropriate depth of the retractor prevents the muscle from intruding into the field of view. The retractor allows for the appropriately sized working channel to permit spinal procedures. METRx system (Medtronic Sofamor Danek, Memphis, TN) was the first commercially available product as a tubular retractor and it is now one of the most widely used tubular retractor systems in the world. The system contains various sizes of dila-

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_18

179

J. U. Lee and D.-H. Kim

180

tors, tubular retractors, and flexible arms. The diameter of tubular retractors varies from 14 to 22  mm and their length varies from 3 to 9  cm. The system also contains various types of instru-

ments that are used in conventional microsurgical spine surgery (Fig.  1). The n­ arrower the tube’s diameter and the longer the tube, the more difficult it is to use surgical tools and obtain sufficient

12.8mm Dilator Flex arm assembly

Flex arm with self-retaining retractors

3cm to 9cm Length 14mm Diameter 14.8mm Dilator

20.8mm Dilator

3cm to 9cm Length 16mm Diameter

3cm to 9cm Length 22mm Diameter (Stainless and Disposable Available) 22.8mm Dilator 16.8mm Dilator

24.8mm Dilator

3cm to 9cm Length 18mm Diameter (Stainless and Disposable Available)

3cm to 9cm Length 26mm Diameter (Stainless and Disposable Available)

18.8mm Dilator 24.8mm Dilator

.062 x 12” 5.3mm Guidewire Dilator

9.4mm Dilator

3cm to 9cm Length 20mm Diameter

Fig. 1  The METRx system contains various sizes of dilators, tubular retractors, and flexible arms. The diameter of tubular retractors varies from 14 to 22 mm and their length varies from 3 to 9  cm. The X-tube retraction system is 4–8 cm in length and 26 mm in diameter (Published with

X-TUBE™ Retraction 4cm to 8cm Length 26mm Diameter (Stainless and Disposable Available)

kind permission of © Medtronic 2022. All Rights Reserved). The system also contains various types of instruments that are used in conventional microsurgical spine surgery. (Published with kind permission of © Medtronic 2022. All Rights Reserved)

Overview of Minimally Invasive Spine Surgery with the Tubular Retractor

Curved Scissors (Standard and Microsizes Available)

40° and 90° Bayoneted Kerrison (1mm, 2mm, 3mm, 4mm, 5mm Available)

2mm Straight and Upbiting Micropituitary

2mm Pituitary with Tooth

4mm Straight and Upbiting Pituitary

2mm Upbiting and Downbiting Pituitary

Wide Nerve Root Retractor

Nerve Root Retractor

Assorted Bayoneted Instruments

Sucker (#6, #8, #10, and Suction Retractor Available)

181

Bayoneted Bipolar Forceps (Standard and MIcrosizes Available)

Angled Bipolar Forceps (Standard and Microsizes Available)

90* Ball Probes Long and Short, Left, Right, and Straight

45* Woodson Probe

Reverse Angled Curettes 1.8mm, 3.6mm, and 5.2mm

Angled Curettes 1.8mm, 3.6mm, and 5.2mm

Straight Curettes 1.8mm, 3.6mm, and 5.2mm

Suction Retractor 90* Dissectors Left, Right, and Straight Nerve Hooks–Straight, Left, and Right (Standard and Microsizes Available)

Penfield Push and Pull (#2, #4, and #7 Sizes Available)

Fig. 1 (continued)

space. However, if too wide tube is used, the more potential there is to damage posterior paraspinal muscles. Bayoneted instruments would be helpful to implement successful manipulation through a restricted corridor of the tubular retractor. Various types of procedures like decompression, microdiscectomy, and interbody fusion can be accomplished through this system. Emerging techniques for advanced reconstruction including posterior corpectomies and strut fusion for burst fractures, tumors, and infections are also possible [2]. The procedures are initiated by inserting a spinal needle into the paraspinal musculature at the appropriate distance off the midline toward the bony anatomy (Fig. 2a). As the bony landmark is not palpable in the paramedian approach, relevant anatomy should be confirmed radiographically before placement of the initial incision to

ensure sufficient access to the legions. The landmarks of docking points would be set up according to the type of procedures (Table 1). Then the spinal needle is removed, and a vertical incision is made at the puncture site. The incision length should match the diameter of the respective tubular retractor. The incision of the fascia is optional to make dilation easier. The guidewire is placed and directed toward the appropriate anatomy under lateral fluoroscopy. It is advanced carefully only through the dorsolumbar fascia, not the ligamentum flavum. Then, cannulated soft tissue dilator would be inserted over the guidewire using a twisting motion. Once the fascia is penetrated, remove the guidewire and advance the dilator down to the bony anatomy (Fig. 2b). After sequential dilation using the next series of dilators over each other, the appropriate tubular retractor is placed and seated firmly on the bony anatomy. The flexible arm is attached to the bed

J. U. Lee and D.-H. Kim

182

a

b

c

Fig. 2 (a) Procedures are initiated by inserting a spinal needle into the paraspinal musculature at the appropriate distance off the midline toward the bony anatomy. (b) The guidewire is placed and directed toward the appropriate anatomy under lateral fluoroscopy and the cannulated soft tissue dilator would be inserted over the guidewire using a

twisting motion. (c) After sequential dilation using the next series of dilators over each other, the appropriate tubular retractor is placed and seated firmly on the bony anatomy. The flexible arm is attached to the bed rail and the selected tubular retractor

Table 1  The landmarks of docking points would be set up according to the type of procedures

rail and the selected tubular retractor (Fig.  2c). Tubular retractors are docked to the spine, and surgery is typically performed using an operating microscope.

Procedure Discectomy, laminectomy, stenosis PLIF Pedicle screws TLIF Cervical foraminotomy Far lateral

Landmark docking point Inferior aspect of the superior lamina Medial aspect of the facet Transverse process/facet junction Lateral aspect of the facet Medial facet/laminar junction Junction of TP and PARS of superior vertebra

2.1 Lumbar Microdiscectomy The tubular retractor was first used for herniation of the intervertebral disc, and even now is the method most often used. The space needed for laminectomy and discectomy for decompression

Overview of Minimally Invasive Spine Surgery with the Tubular Retractor

183

Fig. 3  Intraoperative image and schematic view of a lumbar herniated disc removal using the tubular retractor

is about 15–20  mm. Therefore, tubes with a diameter of 20 mm and a length of 40–50 mm are generally used. After docking the tubular retractor on the inferior aspect of the superior lamina, surgery is typically performed similarly to open surgery using an operating microscope and surgical tools (Fig. 3). Several randomized controlled trials have been performed to compare traditional open microdiscectomy with minimally invasive tubular microdiscectomy [3–5]. These studies all show that tubular microdiscectomy is safe and efficacious compared to well-established traditional techniques. However, clinically significant superiority was not shown, likely reflecting the difficulty in demonstrating differences between the two already successful procedures. In a meta-­ analysis of 6 trials comprising 837 patients, clinical improvements in pain and function were similar in both the minimally invasive and conventional open groups [6].

2.2 Lumbar Decompression The tubular retractor is a good indication for various lumbar stenosis. The foraminal stenosis is approached in the same way as discectomy. For central stenosis, Weiner et al. described that the spinal canal can be approached through a unilat-

eral portal via a hemilaminectomy technique [7]. Decompression of the central canal and contralateral recess can be achieved by angling the tubular retractor dorsally to view the undersurface of the spinous process and contralateral lamina. Therefore, bilateral decompression would be available by adjusting the position of the tubular retractor which is called the “wanding technique” (Fig. 4). Numerous studies have been reported on the efficacy and safety of minimally invasive posterior lumbar decompression [8–10]. Palmer et al. performed bilateral decompressions via unilateral approach using the tubular retractor system for 17 spinal stenosis patients (22 levels) including 8 spondylolisthesis-related spinal stenosis patients. Postoperatively stenosis was absent at 13 levels, mild at seven, mild/moderate at one, and moderate at one. On early (3-month) postoperative X-ray films there was no evidence of further instability in any case. The procedure could be undertaken successfully on an outpatient basis, with reasonable operative times, minimal blood loss, and acceptable morbidity ­ [8]. Asgarzadie and Khoo reported that this technique provides long-term symptomatic relief equivalent to traditional open surgery but with significant reductions in operative blood loss, postoperative pain, hospital stay, and narcotic usage [10].

184

J. U. Lee and D.-H. Kim

Fig. 4  Schematic view of unilateral laminectomy and bilateral decompression by adjusting the position of the tubular retractor. “Wanding technique”

2.3 Far Lateral Approach Using the Tubular Retractor The term “far lateral” is used variably in the literature and usually refers to an extraforaminal displacement in the peridiscal zone peripheral to the sagittal plane of the most lateral part of the pedicle at the same level. This unique anatomy necessitates targeted surgical approaches. A minimally invasive outside-in approach would be able to decompress the nerve root with minimal dissection and morbidity. The paramedian incision is made more laterally than other lumbar procedures and the distance from the midline would be determined by the preoperative imaging. The guidewire is advanced toward the junction of the transverse process and pars interarticularis of superior vertebrae. Then the tubular retractor is docked to bony structures and the medial aspect of the transverse process, lateral aspect of the pars interarticularis, inferior articular facet, superior articular facet, and facet joint line might be identified using the microscope (Fig.  5a). The exiting nerve root decompression or microdiscectomy would be accomplished through the tubular retractor (Fig. 5b). The far lateral microdiscectomy offers the prospect of better long-term results than other surgical techniques like medial facetectomy, laminectomy, hemilaminectomy, and approaches through the pars interarticularis. Knio et al. performed a far lateral tubular decompression for 42

patients and collected a visual analog scale for back pain and leg pain and Oswestry Disability Index (ODI) preoperatively and at the 12- and 24-month follow-ups. They reported back pain, leg pain, and ODI showed significant improvement postoperatively and the improvement was maintained at 2 years [11]. The extraforaminal zone at L5–S1 has several unique anatomical features. The broader pedicle with, coronally oriented and broader facet complex, narrow space between the L5 transverse process and the sacral ala, and the sacroiliac part of the iliolumbar ligaments with its lumbosacral band, create a narrow “lumbosacral tunnel” through which the L5 nerve courses. Therefore, degenerative osteophytes at the lateral aspect of L5 and S1, disc space collapse, coronal wedging, and diffuse, even smaller disc bulges can further narrow this tunnel causing L5 radiculopathy which is called “far-out syndrome.” Surgical access to this zone is difficult, because the wide interpedicular distance, broad pedicles, and facet complex place this zone further laterally, making the midline approach more invasive with longer incisions and extensive muscle dissection. On the other hand, the prominent iliac crest, the coronally oriented and broad facet joints, and the inclination of sacral ala narrow the operative corridor through a posterolateral muscle splitting conventional approach. Minimally invasive surgery using the tubular retractor may overcome the limitations above and can provide easy access to the region with minimal damage to

Overview of Minimally Invasive Spine Surgery with the Tubular Retractor

185

a

b

Fig. 5 (a) Intraoperative imaging shows the process of the tubular retractor placement, landmarks(red), and exiting nerve root(yellow). (b) Intraoperative microscope images of L5–S1 microdiscectomy

the around tissues. Pirris et  al. treated four patients with symptomatic extraforaminal disc herniations at L5–S1 via a minimally invasive, muscle splitting approach with a tubular retractor and operating microscope [12]. All patients had improvement in their preoperative symptoms, and none suffered any intraoperative complications. They reported that the approach provided excellent visualization of the pertinent anatomy while utilizing familiar tools. Lee et al. performed a minimally invasive far lateral approach for extraforaminal decompression of the L5 nerve root using the tubular retractor system for 52 consecutive patients [13]. Fifteen patients (28.8%) complained of postoperative dysesthesias, which were completely resolved in all cases within 6 months. The mean preoperative and postoperative visual analog scale scores were 7.6 and 3.6, respectively. The mean preoperative and postoperative Japanese Orthopaedic Association (JOA) scores were 6.4 and 13.8, respectively. The mean

JOA recovery rate was 86.1%. According to the Macnab functional grading system, 96% of the patients had excellent or good grades at follow-up.

2.4 Transforaminal Lumbar Interbody Fusion Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) would be considered as an extension of the minimally invasive hemilaminectomy technique. The surgical corridor is between the multifidus and longissimus muscle and the tubular retractor system is placed after blunt manual dissection toward the lateral aspect of the facet (Fig. 6a). The expandable retractors like the Quadrant retractor (Medtronic Sofamor Danek, Memphis, TN) can be used instead, for more available space. They can be accommodated to the patient’s anatomy and expand the

J. U. Lee and D.-H. Kim

186

a

b

c

d

Fig. 6 (a) Image showing the blunt manual dissection between multifidus muscle and longissimus muscle. (b) The expandable retractor system. (c) Cage insertion. (d) Percutaneous pedicle screw fixation

exposure when needed (Fig. 6b). By performance of a laminotomy and facetectomy, the ipsilateral nerve root is thoroughly decompressed. Access to the disc space is through a window bordered medially by the dural tube, proximally by the exiting nerve root, and distally by the pedicle and superior endplate of the caudad vertebra thus forming within the Kambin triangle. A large graft can be placed safely with minimal retraction on the thecal sac, which decreases the risk of durotomy and neurological injury (Fig. 6c). The interbody implant should be packed with an appropriate bone graft material, and the space

around the implant should also be filled with graft material. Percutaneous pedicle screw fixation would be inevitably performed in MI-TLIF, to maintain stability until the segment becomes fused firmly (Fig. 6d). Many studies have confirmed the safety and efficacy of this technique [14–16]. Compared to conventional open techniques, MI-TLIF shows less postoperative pain, decreased blood loss, and shorter hospital stays but equivalent symptomatic relief. Several studies also show decreases in deep infection rates with MI-TLIF [17, 18]. Furthermore, it seems that shorter hospital stays,

Overview of Minimally Invasive Spine Surgery with the Tubular Retractor

187

Fig. 7  Removal of both sides of the ossified ligament flavum could be performed by adjusting the position of the tubular retractor

faster return to work, and decreased rates of reoperations due to infections lead to a decreased overall cost of care [19, 20]. Cheng et  al. analyzed 75 consecutive patients who underwent either single-level open TLIF or MI-TLIF and patients were followed up for an average of 5.05  years [21]. Fifty patients underwent MI-TLIF and 25 underwent open TLIF.  They reported that the long-term fusion rate of MI-TLIF (92%) was lower than that of open TLIF (100%). Therefore, many physicians are interested in the use of various graft materials for the improvement of the fusion rate. A ­meta-­analysis showed that a comparison of all recombinant human bone morphogenetic protein (rhBMP) series with all non-rhBMP series showed fusion rates of 96.6% and 92.5%, respectively [22]. The highest fusion rate was observed with a combination of autologous local bone with bone extender and rhBMP (99.1%). The highest fusion rate without the use of rhBMP was seen with autologous local bone plus bone extender (93.1%).

2.5 Thoracic Spine Surgery Tubular retractors are also used in thoracic decompression. Thoracic ossification of the ligament flavum (TOLF) is one of the major causes of thoracic myelopathy in East Asian countries [23]. In the same manner as lumbar decompression, both sides of the ossified ligament flavum in

the thoracic spine would be removed by wanding technique (Fig. 7). The thoracic vertebral alignment is dense and distinguishing the targeted level during surgery is more challenging. Also, the smaller size of thoracic vertebrae would bother physicians when they are performing procedures through restricted corridor of tubular retractor. Therefore, the size and location of the bony opening should be accurate. Zhao et al. performed 3D computer-assisted virtual surgery using 3D reconstruction to calculate the precise location and sizes of the bone window and the angle of insertion of the tubular retractor system [24]. They treated 13 TOLF patients using the tubular retractor system, the mean operative time was 98.23 ± 19.10 min, and the mean blood loss was 19.77  ±  5.97  mL.  At a mean follow-up of 13.3 months (median: 12 months), the mean JOA score was 7.54  ±  1.13 at the final follow-up, yielding a mean RR of 49.10  ±  15.71%. Using the recovery rate, 7 (53.85%) patients had good outcomes, 5 (38.46%) patients had a fair outcomes, and 1 (7.69%) patient had poor outcomes, indicating significant improvement by the final follow-up examination (p 85% at 6 weeks), back pain is selflimiting and resolves with nonsurgical treatment. Surgical treatment is indicated in patients with pain who have clear neurological abnormalities, including weakness, or who do not respond to sufficient conservative treatment for 5–8 weeks [8].

2.1 Microdiscectomy (Interlaminar Approach)

H. Seong Bumin Hospital, Busan, Republic of Korea

2.1.1 Step-by-Step Technique

S. Lim Gumdan Top General Hospital, Incheon, Republic of Korea

Surgical Position 1. In most cases, surgery is performed in the prone position (Fig. 1).

I. Choi (*) Hallym University, Chuncheon, Republic of Korea

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_19

193

194

H. Seong et al.

Fig. 1  Various surgical positions

2. Modified prone position: Hips and knees are bent at 90° with reduced abdominal pressure. 3. Caution: In patients with obesity, lumbar epidural vein dilation could occur due to abdominal compression, increasing the risk of bleeding during surgery. 4. A 3/4 prone or lateral position for the ease of securing the operative field during bleeding. However, the surgeon may not be familiar with the anatomical structure. Preoperative Spine Marking 1. Accurate marking of the surgical sites is essential. 2. In patients with obesity or lumbarization of the sacrum, the surgical site may be inaccurately identified. 3. If the surgical site is unclear, the surgeon must acquire radiographs to ascertain it. Incision 1. A short incision is made on the extension of the midline between the spinous processes of the site of the lesion. 2. A mixture of 0.5% lidocaine and epinephrine is injected into the incision site to reduce bleeding. 3. Subsequently, a self-retaining retractor is used to retract the space between the muscles. This reduces bleeding and facilitates electrocauterization of the bleeding site. 4. Hemostatic forceps are not used during electrocauterization of blood vessels because tissues may be significantly damaged. 5. If the patient is obese, a self-retaining retractor is inserted deeper and reinstalled.

Fig. 2  During subperiosteal dissection, the periosteum must be removed completely from the spinous processes and spinal lamina. If the periosteum penetrates and tears the muscles, bleeding may occur

Subperiosteal Dissection 1. The periosteal elevator applies pressure to the edge of the spinous processes, helping to preserve the posterior spinous and supraspinal ligaments. The preservation of these structures can avoid unnecessary weakening of the supportive ligaments of the spine. 2. The muscles are detached from the spinous processes and spinal lamina. Electrocauterization of the bleeding site with bipolar cautery helps secure the operative field without bleeding. The periosteum must be completely removed from the spinous processes and spinal lamina. If the periosteum penetrates and damages the muscles, bleeding may occur (Fig. 2). 3. Bleeding caused by an incision of the edge of the fascia can be stopped by bipolar cauterization. Subperiosteal muscle dissection is performed laterally to expose the joint between the superior and inferior articular processes. After exposing the medial part of the lamina, facet joint, and spinous process, lateral radio-

Minimally Invasive Spinal Decompression for Lumbar Spine

195

Fig. 3  Installation of a hemilaminectomy retractor to secure a wider operative field

graphs must be acquired to examine the surgical site. Once the correct surgical site is confirmed, the retractor is inserted for bilateral subperiosteal exposure or hemilaminectomy, depending on the surgeon’s preference. The hemilaminectomy spinal retractor has a sharp and thin structure, with the right tip bent in a hook shape. The left side has a large area for traction. A retractor can be inserted with the left-side facing the lateral and upper sides of the articular facet to secure the operative field (Fig. 3). Developing the Interspace 1. The lamina has different widths, angles, and positions. Thus, if the interlaminar space is sufficiently wide, partial removal can expose the disc, or the disc can be removed. 2. A wide interlaminar space is most commonly observed between the fifth lumbar and first sacral vertebrae and is rarely observed in the upper parts. If the interlaminar space is normal, the Kerrison rongeur forceps can be used to remove the lower edge of the protruding superior spinal lamina. If the interlaminar space between the fifth lumbar and first sacral vertebrae is manipulated, the

lower edge of the fifth lumbar lamina is removed. Alternatively, the lower one-third of the posterior lamina may be removed to expose the upper border of the ligamentum flavum (Fig. 4). 3. The ligamentum flavum can be grasped with tissue forceps and the remnant removed. After removing the protruding lower onethird of the superior lamina, the wide ligamentum flavum is exposed. A shallow incision is made in the direction of movement of the ligamentum flavum tissue with surgical scalpel blade no. 11. 4. The edge of the incised area is held with forceps and pulled laterally to widen the incision. A small cottonoid is inserted under the ligamentum flavum to separate it from the dura mater. The incision is widened from the superior to the inferior laminae. While holding the entire ligamentum flavum with the second set of forceps, a curet is inserted into the lower surface of the upper spine. The flap of the ligamentum flavum is exfoliated laterally, and its remnant is left attached to the belly side of the inferior lamina. This remnant can be safely removed using a blade or scissors (Fig. 5).

H. Seong et al.

196 Medial

Cephalad

Upper lamina

Ligament Lower flavum lamina

Medial

Caudal

Cephalad

Lateral

Caudal

Lateral

Fig. 4  Kerrion rongeur forceps being used to remove the lower edge of the protruding superior spinal lamina

a

b

c

d

Fig. 5  Ligamentum flavum removal procedure (a–d)

Minimally Invasive Spinal Decompression for Lumbar Spine

Epidural Fat and Nerve Root Damage 1. After removing the ligamentum flavum, epidural adipose tissue is observed. Preserving the epidural adipose tissue layer surrounding the nerve root helps to prevent scar tissue from enclosing the nerve root when reentering the space. 2. To better expose the nerve root and dura mater, the epidural fat flap is frequently tractioned. The epidural fat is then inserted around the nerve root. If the nerve roots cannot be confirmed and the operative field is not secured while preserving the fat, the fat should be removed. 3. The purpose of surgery is the safe decompression of the nerve root. In this step, the nerve root can be damaged in two ways. 4. A common mistake involves the incorrect identification of the laterally tractioned ligamentum flavum above the nerve root as the nerve root. After a medial incision of the ligamentum flavum, it is rolled laterally into a cylindrical shape, which can be confusing. This cylindrical ligamentum flavum can be tractioned medially, which can cause the nerve root to resemble a swollen disc. Therefore, surgeons may accidentally incise the nerve root (Fig. 6). 5. Another mistake occurs when the medial part of the ligamentum flavum and bone is excised

Lateral Edge of Yellow Ligament

Fig. 6  When the ligamentum flavum above the nerve root is tractioned laterally, the ligamentum flavum is sometimes mistaken for the nerve root

197

as the interlaminar space expands laterally. During this exposure process, extra caution and a good operative field are required to capture the lower ligamentum flavum and bone surface using a punch. If the tip of the rongeur is inserted too deep, the ligamentum flavum and nerve root along the edge of the bone may be grabbed when the surgeon pulls the ­rongeur. This causes distinctly long, shiny white nerve tissues to stick out, followed by cerebrospinal fluid (CSF). These mistakes can be avoided by ensuring proper hemostasis, an adequate operative field, and a careful and slow operation. A 40° angle punch helps to work on the superior lamina and lateral parts. However, this may cause dural lacerations in the lower lamina. Partial resection of the facet joint is essential for exposing the lateral edge of the nerve root. This procedure is painless. When performed unilaterally, this does not cause spinal instability. Bilateral resection of the facet joints can lead to spinal instability and pain. Adequate lateral exposure of the disc leads to less traction on the nerve root and dura mater while granting access to the disc (Fig. 7). Interlaminar Surgery 1. In patients with prolonged symptoms, tight adhesions between the nerve root and posterior longitudinal ligament may occur. The nerve root and dura mater should be carefully dissected for free nerve traction and disc exposure. 2. If there is pressure from the lower part, the nerve root must be pulled medially without resistance. Typically, herniated discs are clearly observed when the nerve root is pulled medially and can be confirmed by slight lifting and medial traction of the nerve root. During this step, the surgeon must be careful not to pull the nerve root. 3. If herniation of the discs is extensive, it is best not to overtract the nerve root. If too much force is required to tract the nerve root medially, the nerve root must be decompressed laterally without traction.

198

H. Seong et al.

Fig. 7  Inadequate lateral bone exposure leads to excessive traction of the nerve root and dura mater. In contrast, adequate lateral bone exposure leads to little traction of the nerve root

4. If the disc fragment is free within the spinal canal, manipulation can be performed on the lateral side. The disc is then removed using pituitary forceps. 5. If the disc is not herniated and swollen and if the nerve root does not move inward easily, the surgeon must partially decompress the outer part of the annulus fibrosus by working laterally to easily tract the nerve root and remove the disc fragments gradually. 6. Swollen and inflamed nerve roots are already damaged by disc herniation. Thus, traction must be minimized to prevent further damage. 7. Disc herniation may occur at the medial end. Subsequently, the nerve root may not be elevated or there may be no compression underneath. However, if medial traction is impaired, the nerve root and dura mater must be carefully lifted to ensure that the herniated disc is in the medial area. Intervertebral Disc Excision 1. Once the intervertebral disc is partially resected, the nerve root can be retracted medially without difficulty. As a result, retraction

of the nerve root becomes more secure when exposing the intervertebral disc space. 2. Using surgical blade no. 11, a rectangular opening is made in the annulus fibrosus. The intervertebral disc is sub-resected through the open space. This opening extends from the innermost part of the exposed annulus ­fibrosus to the lateral part, where the bones are exposed over the entire width of the intervertebral disc and are limited by the upper and lower vertebral bodies (Fig. 8). 3. Pituitary forceps have various sizes and shapes for pulling out soft fragments of the intervertebral disc freely. 4. Rectangular resection of the annulus fibrosus prevents buckling of the remaining shell of the annulus fibrosus as the intervertebral disc space narrows. This buckling must be prevented, as it may become fibrotic, causing postoperative nerve root compression. 5. When intervertebral disc rongeur forceps are used in the intervertebral disc space, absolute caution must be exercised to avoid penetrating the anterior intervertebral disc and damaging the common iliac artery, aorta, and vena cava (Fig. 9).

Minimally Invasive Spinal Decompression for Lumbar Spine

199

Fig. 8  Surgical blade no. 11 being used to make a rectangular opening in the annulus fibrosus and remove the disc through this open space

Fig. 9  Intervertebral disc resection using pituitary forceps

Removal of Intervertebral Disc Fragments 1. Herniated intervertebral discs in the axilla between the nerve root and dura mater must be carefully dissected to avoid damage to the laterally dislocated nerve root. 2. Fragments of herniated intervertebral discs from the axillary region closely resemble epidural fat and are hidden medial to the dura mater. Therefore, fragments must be carefully assessed and identified. 3. To remove these intervertebral disc fragments, the nerve root and dura mater are tractioned

medially to expose the moving disc fragments and the swollen or protruding annulus fibrosus. Using a nerve hook, the area around the nerve root is examined to identify and remove herniated intervertebral disc fragments (Fig. 10). Considerations During Surgery 1. If there is no intervertebral disc herniation severely compressing the nerve root during surgery and if only swelling is observed, only posterior nerve root decompression, such as foraminotomy, is performed.

200

H. Seong et al.

Suture 1. Prior to suturing, the removal site of the intervertebral disc is irrigated using saline. 2. During irrigation, any disc fragments that were not seen below the removal site must be assessed. The remaining disc fragments must be cleaned, and future infections must be prevented. 3. Using vicryl 2-0, the muscles and fascia are sutured, and vicryl 3-0 is used to suture the subcutaneous layer. The skin is then sutured using a staple.

2.2 Paraspinal Microdiscectomy (Far Lateral Approach)

Fig. 10  Herniated intervertebral disc fragments being removed after carefully evaluating the area around the nerve root using a nerve hook

2. If there is no intervertebral disc compressing the nerve root, the intervertebral disc must not be damaged. The swollen annulus fibrosus does not need to be removed, especially when the nerve root is decompressed. 3. The nerve root is easily bent without compressing the bone structures, and a simple foraminotomy may be sufficient.

1. Anesthesia: General anesthesia is recommended, as the operation time may be prolonged. Preoperative antibiotic treatment is required. 2. Positioning: The positioning of the patient is similar to that in general lumbar discectomy but may change depending on the surgeon’s preference. Reducing abdominal pressure helps prevent venous congestion, and proper positioning of the patient can increase the intertransverse space. 3. Radiographic labeling: C-arm is recommended to save time. In the lateral view, markings can be labeled on the opposite side of the skin incision to avoid CSF leakage and hematoma in the surgical track. A spine needle is inserted 90° about a finger away toward the lower margin of the disc space, and a horizontal line is drawn. In the anteroposterior (AP) view, a blunt K-wire is placed on the same side of the skin incision, and two horizontal and two vertical lines are drawn. In addition, a horizontal line is drawn on the lower border of the disc space and a horizontal line on the lower border of the transverse process above the disc space. A vertical line connecting the midline and lateral boundary of the segmented pedicle above and below the corresponding disc space is drawn using the spinous process (Fig. 11).

Minimally Invasive Spinal Decompression for Lumbar Spine

201

Fig. 11  Preoperative radiographic labeling of an extraforaminal disc herniation L3/L4 on the left side top lateral fluoroscopic view. Bottom AP view with the patient already positioned

4. Soft tissue dissection: A 3–4 cm long skin incision is performed approximately 5–8 cm from the midline. Fascia is induced using sharp dissection. The plane between the multifidus and longissimus muscles is bluntly dissected, and a

Caspar speculum retractor is installed. A long blade is placed on the longissimus muscle and a short blade on the dorsal side of the multifidus muscle and facet joints to secure the extraforaminal compartment. The transverse

H. Seong et al.

202

2.3 Unilateral Approach Bilateral Decompression (ULBD) 2.3.1 Step-by-Step Technique 15°

b

c

bc

a

a

Surgical Equipment and Instruments Serial insertion of dilators and tubular retractors has many advantages over subperiosteal dissection of muscles from bone tissue, which reduce pain and denervation of paraspinal muscles.

1

Surgeon Position

5 2 3

4

3 15°

Fig. 12  The combined tilting of the microscope and operating room table facilitates the overview of the extraforaminal area, mostly avoiding any bony removal from the facet joint. (1) m. sacrospinalis, (a) m. multifidus, (b) m. longissimus, (c) m. iliocostalis; (2) m. intervertebralis; (3) m. psoas major; (4) intervertebral disc; (5) disc herniation

processes of the lower and upper segments are exposed. The lateral side of the pars interarticularis is the medial boundary of the operative field. The risk of an incorrect level is reduced by radiography during surgery. 5. Microscopic decompression: Tilting the operative table by approximately 15–20° from the surgeon further exposes the lateral part of the pedicle. Drilling of bone tissue is usually unnecessary (Fig. 12). 6. However, if there is hypertrophy of the facet joint or at the L5–S1 levels, drilling may be helpful. As the medial half of the intertransverse muscle is incised and pushed laterally, the intertransverse membrane becomes visible. Incising this membrane exposes the fat surrounding the nerve (Fig. 13).

1. When lower extremity pain is predominantly unilateral, some surgeons prefer to perform the operation while standing on the side of the lesion, while others argue that it is more effective to stand on the opposite side. Based on our observations, those with less experience are better able to perform the operation standing on the side of the lesion. 2. The curved direction of the spinous process is also helpful in determining the ideal position of the surgeon. If a spinous process is curved to the left, an approach from the right makes it easier to install the retractor and widen the operative view. 3. If all the conditions are the same, a right-­ handed surgeon may perform the surgery better when standing on the left side of the patient. Incision

At the more distal lumbar level, the incision is marked farther to the midline, approximately 1–3 cm away (Fig. 14). A 1.5–2 cm longitudinal incision is made using lateral fluoroscopy. Exposure

Bovie cautery is used to make an incision in the lumbodorsal fascia. A guidewire is inserted into the target site and touches the lower part of the superior lamina of the lesion segment, which is

Minimally Invasive Spinal Decompression for Lumbar Spine

a

c

203

b

d

e

Fig. 13 (a–e) Transmuscular far lateral discectomy. (a) After checking the level with C-arm, a 3–4 cm incision is made 5–8 cm away from the midline to include the pars interarticularis. (b) Surgical landmarks, such as the isthmus, transverse process, and intertransverse ligament, are clearly exposed. (c) Using a high-speed drill, bone tissue

is removed in a semi-circular shape, including the superior aspect of the isthmus and inferior portion of the rostral transverse process. (d) The nerve is laterally retracted using a blunt microinstrument to examine the medial side of the nerve. (e) After opening the disc space, limited discectomy is performed

the laminar facet junction (Fig.  14). When a guidewire and the first and second dilators are inserted, the surgeon should be careful to ensure that the bone is untouched. Otherwise, the guidewire may enter the interlaminar space, causing durotomy. Under lateral fluoroscopic guidance, insertion while rotating the dilator is safer. For the final retractor, up to 24  mm in size can be used, which is larger than that used for discectomy. When installing the final retractor, the surgeon should expose the following parts: the bottom half of the superior lamina on the top side, a part of the superior area of the lower lamina, the spino-lamina junction on the medial side,

and the medial half of the facet joint on the lateral side (Fig. 15). A tubular retractor is secured to a table-mounted arm. Laminectomy Ipsilateral Laminectomy

Since the scope of laminectomy for stenosis is the same as that for the ligamentum flavum (LF), it would be helpful to understand the overall anatomy of the LF. The LF covers 70% of the superior lamina toward the top and approximately 10–20% (5 mm) of the upper part of the inferior lower lamina toward the bottom. (2) In some cases, the LF is connected to another LF

H. Seong et al.

204

on the contralateral side at the midline. In other cases, there is a gap, so the surgeon should be careful not to cause durotomy during decompression while drilling the midline. It extends laterally to the superior articular process (SAP) (Fig. 16). Laminectomy is performed using a high-speed drill; however, drilling should be performed only to extract the LF. Excessive removal of the lateral part of the lamina may fracture the pars interarticularis toward the top and damage the facet joint toward the bottom; therefore, careful operation is required (Fig. 16b). Contralateral Laminectomy

Fig. 14  The lamina becomes larger moving down, such that the target site becomes farther from the midline. Thus, the incision site also moves proportionally to the side

Fig. 15  Final retractor image. Sup.—half of the upper lamina, Lat.—half of the facet, the upper part of the lower lamina, Med.—spino-lamina jx

Ideally, the ipsilateral LF will not be removed after ipsilateral laminectomy because it could be a safety bed for drilling the contralateral lamina. After tilting the patient to the contralateral side, a tubular retractor must be tilted toward the contralateral side (Fig.  17a). Drilling should be performed on the lower part of the contralateral lamina and the LF from the contralateral lamina. The lower part of the interspinous ligament should be removed using Bovie cautery and a Kerrison punch, followed by the removal of the inferior lamina by approximately 5  mm where the LF was covered (Fig. 17b). Once laminectomy for the medial facet area on the contralateral side is completed (Fig.  17c), curettes or Penfield dissectors are used to dissect the LF from the dura, followed by LF removal using a Kerrison punch. Because the dura blocks the contralateral traversing root, the contralateral view should be secured by pressing the dura using a suction tip. Because the traversing root and LF are pressed by the hypertrophied facet, a Kerrison punch should be inserted along the root direction after the dissection and subsequently removed. Some studies reported that the contralateral exiting root can be decompressed. While it is difficult to decompress the entire foramen, it is possible to decompress a part of the foramen exiting the root; thus, the far lateral approach is better for this purpose because ULBD is used for both central and lateral recess decompression.

Minimally Invasive Spinal Decompression for Lumbar Spine

a

205

b

Fig. 16 (a) The LF covers 70% of the superior lamina toward the top and approximately 10–20% (5 mm) of the upper part of the inferior lamina toward the bottom. The SAP is covered on the lateral side. The LF can be con-

nected to another LF on the midline or the two can be separated by a gap. (b) Orange-simple laminectomy, red-­ extend midline, black-preserved pars interarticularis, gray-preserved facet joint

Ipsilateral Lateral Recess Decompression

surgeons should attempt to preserve the facet joint as much as possible by undercutting the SAP. Since ULBD generates more empty spaces than discectomy, surgeons should be vigilant about controlling bleeding to prevent hematoma. Floseal, a gel foam with fibrin for venous bleeding and bone wax for cancellous bone bleeding can be used.

After contralateral decompression, the patient should be adjusted to a neutral position, and the tubular retractor erected to its original position (Fig. 18). The ipsilateral LF and dura are dissected using a Penfield dissector, and the LF is removed using a Kerrison punch. The medial part of the facet joint is partially removed to decompress the ipsilateral lateral recess zone. During facetectomy,

H. Seong et al.

206 Fig. 17 (a) Tilting table and wanding retractor. (b) As in the ipsilateral lamina, parts of the superior and inferior lamina on the contralateral side should be removed. Removal of the lower interspinous ligament facilitates the removal of the inferior lamina and SAP on the contralateral side. (c) After the completion of the contralateral laminectomy

a

b

c

Minimally Invasive Spinal Decompression for Lumbar Spine

Fig. 18  Table neutral and erecting retractors

3 Postoperative Consideration and Case Illustration

207

the possibility of infection increases; therefore, it is necessary to tightly close the fascia layer. In MIS, the incision is small, and blood loss is minimal; therefore, the risk for hematoma is low. Coagulopathy and peri-operative hypertension are known risk factors of hematoma [17–19]. In the presence of hematoma after surgery, the patient may complain of neurological changes or severe back and radiative pain in the lower extremities. Therefore, it is necessary to perform urgent magnetic resonance imaging to localize and remove the hematoma. Although it is rare to find a clear bleeding focus in the operative field, it is necessary to check for bone or arterial bleeding. MIS is associated with a lower infection rate than open surgery. Lesser tissue injuries and the small incision size lead to a lower infection rate. Treatment for postoperative spinal infections has not been standardized. Treatment with broad-­ spectrum antibiotics should be initiated after adequate culture specimens are obtained.

3.1 Complications

3.2 Case Illustration

Compared to open surgery, MIS has advantages in terms of blood loss, postoperative pain, recovery, and the length of hospital stays [9, 10]. However, since the learning curve is steep, several complications can occur, especially for beginners [11–15]. The most common complication is CSF leakage after durotomy [13, 14, 16]. To prevent incidental durotomy, the LF must be preserved until the drilling work is finished. When CSF leakage occurs, primary closure may be difficult in a narrow operative space. Experienced surgeons can attempt primary closure, but beginners can damage the dura while attempting primary closure; therefore, it might be better to use fibrin glue, muscle patchy, or gel foam. The Valsalva maneuver can be used to confirm whether the repair was successful. CSF drainage may be considered if CSF leak persists. If the CSF wets the gauze covering the wound,

A 59-year-old man presented with radiating pain in both lower legs and claudication, both of which had lasted for several years. Left and right symptoms were similar. The spinous process was straight rather than inclined. The leftside approach was familiar; therefore, a skin incision was made 3 cm lateral to the midline. Serial tubular retractors were installed. The ipsilateral lamina, contralateral inferior cortical bone of the lamina, and the LF on both sides were removed. Attempts were made to save the rest of the structure, including the SAPs particles on both sides, and he could walk the next day after surgery; all symptoms resolved. The central and lateral recess areas were decompressed on postoperative magnetic resonance imaging (Fig. 19). The retractor is installed obliquely and into a spinous process, and both facet joints are preserved.

H. Seong et al.

208

a

b

Fig. 19 (a) Preoperative images. (b) Postoperative images

4 Summary Surgical methods using tubular systems and microscopes have been developed over the past few decades. To date, it is the most commonly used standard procedure in this field. The time and experience of the surgeon determine the outcome; therefore, it is an important technique.

References 1. Wilkins W.  Separation of the vertebrae with protrusion of hernia between the same. Oper Cure St Louis Med Surg J. 1888;54:340–1. 2. Olszewski AD, Yaszemski MJ, White AA 3rd. The anatomy of the human lumbar ligamentum flavum. New observations and their surgical importance. Spine (Phila Pa 1976). 1996;21(20):2307–12.

Minimally Invasive Spinal Decompression for Lumbar Spine 3. Hibbs R. An operation for progressive spinal deformities. N Y Med J. 1911;93:1013–6. 4. Albee F. Transplantation of a portion of the tibia into the spine for Pott’s disease: a preliminary report. J Am Med Assoc. 1911;57:885–6. 5. Verbiest H. A radicular syndrome from developmental narrowing of the lumbar vertebral canal. J Bone Joint Surg Br. 1954;36-b(2):230–7. 6. Poletti CE.  Central lumbar stenosis caused by ligamentum flavum: unilateral laminotomy for bilateral ligamentectomy: preliminary report of two cases. Neurosurgery. 1995;37(2):343–7. 7. Weiner BK, Walker M, Brower RS, McCulloch JA. Microdecompression for lumbar spinal canal stenosis. Spine (Phila Pa 1976). 1999;24(21):2268–72. 8. Fager CA.  Observations on spontaneous recovery from intervertebral disc herniation. Surg Neurol. 1994;42(4):282–6. 9. Mobbs RJ, Li J, Sivabalan P, Raley D, Rao PJ.  Outcomes after decompressive laminectomy for lumbar spinal stenosis: comparison between minimally invasive unilateral laminectomy for bilateral decompression and open laminectomy: clinical article. J Neurosurg Spine. 2014;21(2):179–86. 10. Khoo LT, Fessler RG.  Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery. 2002;51(5 Suppl):S146–54. 11. Phan K, Mobbs RJ. Minimally invasive versus open laminectomy for lumbar stenosis: a systematic review and meta-analysis. Spine (Phila Pa 1976). 2016;41(2):E91–E100. 12. Ahn J, Iqbal A, Manning BT, et al. Minimally invasive lumbar decompression-the surgical learning curve. Spine J. 2016;16(8):909–16.

209

13. Alimi M, Njoku I Jr, Cong GT, et al. Minimally invasive foraminotomy through tubular retractors via a contralateral approach in patients with unilateral radiculopathy. Neurosurgery. 2014;10(Suppl 3):436– 47; discussion 46–7. 14. Alimi M, Hofstetter CP, Pyo SY, Paulo D, Härtl R.  Minimally invasive laminectomy for lumbar spinal stenosis in patients with and without preoperative spondylolisthesis: clinical outcome and reoperation rates. J Neurosurg Spine. 2015;22(4):339–52. 15. Parikh K, Tomasino A, Knopman J, Boockvar J, Härtl R. Operative results and learning curve: microscope-­ assisted tubular microsurgery for 1- and 2-level discectomies and laminectomies. Neurosurg Focus. 2008;25(2):E14. 16. Wong AP, Shih P, Smith TR, et  al. Comparison of symptomatic cerebral spinal fluid leak between patients undergoing minimally invasive versus open lumbar foraminotomy, discectomy, or laminectomy. World Neurosurg. 2014;81(3-4):634–40. 17. Kou J, Fischgrund J, Biddinger A, Herkowitz H. Risk factors for spinal epidural hematoma after spinal surgery. Spine (Phila Pa 1976). 2002;27(15):1670–3. 18. Fujiwara Y, Manabe H, Izumi B, et al. The impact of hypertension on the occurrence of postoperative spinal epidural hematoma following single level microscopic posterior lumbar decompression surgery in a single institute. Eur Spine J. 2017;26(10):2606–15. 19. Yamada K, Abe Y, Satoh S, Yanagibashi Y, Hyakumachi T, Masuda T.  Large increase in blood pressure after extubation and high body mass index elevate the risk of spinal epidural hematoma after spinal surgery. Spine (Phila Pa 1976). 2015;40(13):1046–52.

Minimally Invasive Spinal Decompression for Cervical Spine Chang-Il Ju and Se-Hoon Kim

1 Introduction Cervical radiculopathy may result from compression of the nerve root due to disc herniation or degenerative stenosis with osteophyte formation in the cervical intervertebral foramen. Surgical decompression is an effective treatment method when conservative methods fail to relieve pain or when significant weakness occurs in the upper extremity muscles supplied by the compressed nerve root [1–3]. Anterior cervical discectomy and fusion (ACDF) and cervical artificial disc replacement (TDR) were the standard of care of reference [4]. Morbidity due to anterior cervical spine surgery ranged from 13.2% to 19.3%, and pseudoarthrosis and adjacent segment disease were the most common postoperative complications [5]. Foraminotomy, either from anterior or posterior, is an alternative surgical procedure for direct nerve root decompression in cervical radiculopathy [4– 6]. It has been reported that anterior cervical foraminotomy (ACF) is a safe and feasible “functional surgery” for direct nerve root decompression with preservation of the motion segment [4, 5]. C.-I. Ju (*) Department of Neurosurgery, Chosun University Hospital, Gwangju, Republic of Korea e-mail: [email protected] S.-H. Kim Department of Neurosurgery, Ansan Hospital, Korea University Medical Center (KUMC), Ansan, Republic of Korea

Furthermore, ACF does not require stabilization, which allows the surgeon to circumvent fusion-related complications including pseudarthrosis and to lower the costs [7]. Since the first description from Jho [4] in 1996, this technique remained controversial and has not been widely adopted by surgeons as a valid alternative to ACDF despite the satisfactory results in terms of safety and feasibility of ACF as a treatment for cervical radiculopathy [5, 8–15]. A major concern limiting the acceptance of ACF is the risk of vertebral artery (VA) injury [8, 12]. Posterior cervical foraminotomy has become increasingly popular as an alternative to ACDF, reducing problems associated with fusion, and has the added benefit of preserving motion with equally good clinical outcomes [13–15]. Posterior cervical foraminotomy is a motion-­ preserving technique first described by Spurling and Scovillein 1944 [16]. Today however it can be done using advanced minimally invasive techniques that minimize incisions, result in less bleeding, and provide an effect equivalent to open surgery, significantly reducing the length of hospital stay and return to daily activities after surgery. In addition, the treatment cost is also reduced [17–19]. In this chapter, the authors did their best to help the reader understand the minimally invasive surgical technique for cervical radiculopathy by presenting an overview of cervical nerve decompression and a brief review of surgical indications, outcomes, and other related issues.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_20

211

212

2 Anatomical Consideration Patients with cervical radiculopathy may have narrow neural foramen because of osteophyte accumulation or hypertrophy of the uncovertebral joints. For those patients who suffered from neural foraminal stenosis, uncinate resection performed with ACDF could achieve a better outcome. In the case of myelopathy, decompression between both uncinated process is sufficient; however, in case of radiculopathy, more lateral decompression is required to decompress the neural foramen. This may put the nerve root and vertebral artery near the uncinated process at great risk. The cervical intervertebral foramen extend from the inferior aspect of the pedicle to the superior aspect of the pedicle of the inferior vertebrae. The anterior wall of the foramen is formed by the uncinate process, the posterolateral aspect of the intervertebral disc, and the adjoining vertebral body. The facet joint along with the superior articular process of the lower vertebra forms the posterior wall of the foramen. The nerve root enters the foramen medially at the medial border of the rostral and caudal pedicle and exits the foramen laterally as it passes the lateral margin of the rostral and caudal pedicles. In the sagittal oblique plane, the nerve roots are seen to lie below a line drawn from the tip of the uncinate process to the tip of the superior articular process. The V-point (including the inferior margin of the cephalic lamina, the medial junction of the inferior and superior facet joints, and the superior margin of the caudal lamina) is the anatomical landmark for the beginning of bone drilling [13, 14]. In the middle-aged group, the dura width and the interlaminar width decreased in the same direction so that we can predict the relative position between the lateral dura edge and the V-point with less remarkable errors. In the old-aged group (the 70s), significant changes in two parameters were found, the dura width increased in the C4–5, C5–6, and C6–7 levels, but interlaminar width decreased according to aging. These results mean that the lateral dura edge would be more laterally located than the V-point in the C4–5, C5–6, and C6–7 levels, considerable attention is required not to injure the nerve structures [15]. Another essential considering point is the surgical position of the cer-

C.-I. Ju and S.-H. Kim

vical spine curvature. Insufficient neck flexion induces the V-point moves to more medially, and insufficient bony removal would be done than the predicted extent [15].

2.1 Anterior Cervical Microforaminotomy 2.1.1 Indication and Contraindication 1. Indications –– Patients with cervical radiculopathy, myelopathy, or myeloradiculopathy –– Anterolateral pathology such as disc herniations or anterior osteophytes –– Lesions of the vertebral artery or foramen transversarium –– Progressive neurologic decline or failure of at least 3  months of conservative management 2. Contraindications –– Posterior pathology and centrally located anterior pathology –– Instability –– Ossification of Posterior longitudinal Ossification (OPLL) 2.1.2 Step-by-Step Technique Step 1. Patient Position After induction of general anesthesia by endotracheal intubation, the patient is supine on the operating table in a manner similar to standard anterior cervical discectomy (ACD). No cervical traction device or fixation of the upper extremity was used. Place a low pillow behind the neck and extend the patient’s neck slightly posteriorly (Fig. 1). Step 2. Skin Incision and Dissection After drawing an imaginary line along the midline of the patient’s neck and the leading edge of the sternocleidomastoid muscle, first, the anterior tubercle of the transverse process of the sixth cervical vertebrae is prominent. A portable fluoroscopy is sometimes used to confirm a more accurate location. At the leading edge of the sternocleidomastoid muscle, make an incision in the skin about 2 cm inward and 1 cm outward along the skin fold direction for a total of 3 cm in total. The location of the

Minimally Invasive Spinal Decompression for Cervical Spine

skin incision differs according to each surgical method. In the case of the transcopreal approach, it is helpful to make an incision about 1 cm above the incision line of the transuncal approach, when performing skin traction or foraminotomy. The method to reach the anterior part of the vertebral body is the same as the general anterior cervical approach. After careful dissection and spreading the fascia forming the inner boundary of the sternocleidomastoid muscle, use your fingers to carefully widen it between each muscle. After confirming the heartbeat by palpating the carotid artery with a finger, position it outward so as not to injure it, and then dissect the longus colli muscle located in the anterior part of the vertebral body internally, then the retractor is firmly installed to position the carotid artery out-

213

ward and the esophagus and airway inward. In order to confirm the exact location once more, a portable fluoroscopy is used. Step 3. Foraminotomy with Nerve Decompression Transuncal Approach

Fig. 1  Patient position and skin incision

If the surgical site is accurately identified, the first and most important step is to identify the lateral boundaries of the vertebral bodies using palpation or a single-ended elevator and then to confirm the boundaries of the upper and lower transverse processes. This is because the uncus is located between the upper and lower transverse processes and this is the target point. Then, make a window by cutting the inner part of the longus colli muscle in the area where the intervertebral foramen is to be expanded. If bleeding occurs, use an electric cauterizer to stop the bleeding. If you become more familiar with the technique later, you can do surgery after exposing the uncus by spreading the longus colli muscle just above the uncus without cutting the longus colli (Fig. 2). The origin of cervical neuroforaminotomy begins at the junction between the uncus and the vertebral body, and after removing the uncus, the nucleus pulposus or osteophytes pressing on the nerve root are removed. During surgery with this method, the hole at the origin of foraminotomy often tended to be located a little lower than the lesion site. This is because the anatomical structure of the cervical

Fig. 2  Dissect the longus colli muscle located in the anterior part of the vertebral body internally, then the retractor is firmly installed to position the carotid artery outward

and the esophagus and airway inward. Then, make a window by cutting the inner part of the longus colli muscle in the area where the intervertebral foramen is to be expanded

C.-I. Ju and S.-H. Kim

214

intervertebral disc is cephalic inclination in the sagittal plane. Therefore, when the intervertebral foramen is fully expanded and the posterior portion of the uncus is removed during surgery with this method, the anterior and superior portion of the cervical vertebra was often exposed. In addition, the lateral portion of the intervertebral disc located in front of the uncovertebral junction had to be removed to some extent. Therefore, this method is still used when a wider surgical field of view is needed, such as spinal decompression or intradural tumor removal, but in the treatment of unilateral radiculopathy, it can be operated by switching to the upper vertebral transcoporeal approach (Fig. 3).

pulposus and osteophytes without removing the anterior portion of the uncus. In other words, nerve root decompression can be achieved by removing only the posterior 1/3 while preserving the anterior 2/3 of the intervertebral disc as much as possible during foraminotomy (Fig. 4). Confirmation of Decompression and Decision to End Surgery

One thing many surgeons always worry about when performing a cervical foraminotomy is when to end the operation. The surgeon person-

Upper Vertebral Transcorporeal Approach (UVTC)

Since the cervical disc is inclined toward the head in the sagittal plane, the origin of foramen dilatation should be moved more cranially than the uncovertebral junction. Its position is the lower left of the upper vertebral body. If you start from here and extend posteriorly and adjust the angle toward the intervertebral disc, the intervertebral foramen in which the nerve root is located is immediately exposed. In this way, nerve root decompression can be achieved by removing the prolapsed nucleus a

b

Longus colli

LCM

c

Nerve root

VA Uncinate process

Fig. 4  Illustration showing the various entry and resection sites of microforaminotomy. (A) Entry point of upper transcorporeal approach. (B) Resection site of transuncal approach. (C) Entry point of lower transcorporeal approach

Disc

3mm

Longus colli

Disc PLL fragment

Fig. 3 Microsurgical anterior cervical foraminotomy (uncoforaminotomy) for unilateral radiculopathy. (a) After removing the longus colli muscle, remove the uncus about 3  mm downward from the disc using a drill, when the intervertebral foramen is fully expanded and the posterior portion of the uncus is removed. (b) The nerve root pressed

behind the disc fragment is identified by removing the upper cervical body with gerrison punch. (c) Using a nerve hook, carefully extract the disc fragment and decompress the nerve root. LCM longus colli muscle, UP uncinate process, VA vertebral artery, D disc, NR nerve root, DF disc fragment, PLL posterior longitudinal ligament

Minimally Invasive Spinal Decompression for Cervical Spine

ally removes the osteophyte or prolapsed nucleus pulposus that is pressing the nerve root, checks for defects in the posterior longitudinal ligament, and removes a part of the posterior longitudinal ligament to check for the presence of the nucleus pulposus prolapsed into the spinal canal. However, when the posterior longitudinal ligament incision is made, bleeding may delay the operation, but the incision does not always occur. Finally, after the final confirmation of the presence of nuclear fragments or bone spurs remaining along the nerve root using a fine probe, if the compressed nerve root swells back toward the operator, the operation is terminated when the heartbeat can be seen.

2.1.3 Postoperative Consideration and Case Illustration Complications –– Hoarseness of voice due to recurrent laryngeal; nerve injury –– Vertebral artery injury –– Carotid artery and jugular vein injury –– Esophageal perforation –– Airway injury –– Thoracic lymphatic duct injury –– Horner syndrome due to sympathetic chain injury –– Spinal instability –– CSF leakage –– Neve root or spinal cord injury Case Illustration (Fig. 5) a

b

Fig. 5 Postoperative axial CT and MR images. (a) Immediate postoperative axial CT image showing foraminotomy on the right side. (b) Postoperative sagittal MR

215

2.2 Posterior Cervical Foraminotomy 2.2.1 Indication and Contraindication The clinical indications 1. Cervical radiculopathy with defined neurologic disturbance (sensory disorder, reflex abnormality, motor weakness) 2. Cervicogenic headache or discogenic axial pain from soft cervical disc herniation 3. Persistent cervical radiculopathy after nerve root block 4. Unsuccessful conservative therapy for at least 6 weeks The radiologic indications 1. Cervical disc herniation around foraminal area demonstrated on computed tomography (CT) and/or magnetic resonance imaging (MRI) 2. No definite segmental instability on dynamic radiography (flexion-extension view) 3. Foraminal stenosis with disc space narrowing The contraindications 1. Ossification of the posterior longitudinal ligament or cervical stenosis 2. Myelopathy or severe neurologic deficit 3. Cervical spondylolisthesis or segmental instability 4. Other pathologic conditions, such as fracture, tumor, or active infection c

image shows foraminotomy and decompression of the C5–6 neural foramen. (c) Postoperative axial MR image shows foraminotomy on Rt C6–7 neural foramen

216

2.2.2 Step-by-Step Technique The procedure is performed with the patient under general anesthesia and in the prone position with the head fixed in a three-point skull clamp. The microscope is used to optimize illumination and visualization. Step 1. Position and Localization The patient maintains the posture with the neck in a neutral or slightly flexed position to allow the cervical spine to relax (Fig.  6). The bed is adjusted so that the head lies above the heart to reduce the amount of venous bleeding. Typically, the table is tilted into reverse Trendelenburg to distribute blood into the abdomen and legs thereby creating a more physiologic state for the patient and providing better visualization in the operative field. To facilitate this position, the head of the table is placed on the top rung, and the foot of the bed is placed on the bottom rung. A metal instrument or a spinal needle is used to identify the target level with lateral fluoroscopy. The dorsal facet joint represents a good target for localization. Once the correct level is identified, a 2.5  cm linear incision is marked approximately 2 cm off midline. Step 2. Serial Dilation and Placement of Tubular Retractor After placing the first tubular dilator on the lamina through the dissection plane, sequential dilation is performed using a series of dilators of enlarging diameter. Once the 18-mm dilator is passed, the working depth can be determined and the appropriate 18-mm tubular retractor should Fig. 6  Reverse Trendelenburg position for posterior cervical foraminotomy. The patient is placed in the prone position with the cervical region elevated above the level of the right atrium to reduce venous pressure. Head fixation is by Mayfield tongs

C.-I. Ju and S.-H. Kim

then be passed over the dilators and secured to the rigid table arm. Lateral fluoroscopy is used to confirm the appropriate level (Fig. 7). Exposure of the inferior half of the cranial lamina, superior border of the caudal lamina, base of the spinous process, and laminofacet junction are required (Fig. 7). Identifying the triangle created by the two laminae and facet joint is a helpful anatomic landmark. Step 3. Ipsilateral Laminotomy The V-point (including the inferior margin of the cephalic lamina, the medial junction of the inferior and superior facet joints, and the superior margin of the caudal lamina) is the anatomical landmark for the beginning of bone drilling (Fig. 8). Using a high-speed diamond drill and Kerrison rongeur, an open laminoforaminotomy is performed to create a working window that can enter the foramen. The remaining muscle over the bone is removed by using the pituitary rongeur. Using a high-speed diamond burr, initiate the laminoforaminotomy under a microscope or endoscope. The assistant surgeon provides irrigation while the primary surgeon is burring. Uniformly remove the even amount of cranial and caudal lamina, starting at the junction of the lamina and facet medially and working laterally toward the facet joints (Fig. 9). Identify the medial and cranial margins of the pedicle that orient in relation to the neural foramen. Continue the foraminotomy until the lateral margin of the pedicle begins to fall off. At this point, approximately 1/3 to 1/2 of the medial side of the facet should be removed (Fig. 10). A small amount of removing the caudal lamina can be used to improve visualization of

Minimally Invasive Spinal Decompression for Cervical Spine

a

217

b

c

Fig. 7 (a) Tubular dilators (18 mm) are used to spread the paraspinal muscles. (b) The soft tissue is removed, exposing the medial half of the facet joint and the inferior

portion of the superior lamina. (c) In microscopic view, the inferior articular process (IAP) of the cephalad vertebrae is identified in C5–6 level

Fig. 8  Posterior cervical foraminotomy. The extent of the “keyhole” prior to foraminotomy. The V-point (including the inferior margin of the cephalic lamina, the medial junction of the inferior and superior facet joints, and the superior margin of the caudal lamina) is the anatomical landmark for beginning of bone drilling

Fig. 9  Right-angle rongeur beginning the “keyhole” opening. Drilling on about 3–5 mm diameter of superomedial corner of the medial aspect of superior articular facet of lower vertebra lying close to the dorsal aspect of the nerve root, which leads to the proximal portion of the nerve root

218

Fig. 10  Approximately 1/3 to 1/2 of the medial side of facet should be removed. 3–5 mm diameter of bone was removed in a circular fashion from the lateral inferior aspect of the upper lamina followed by approximately 3 mm of the medial inferior portion of upper facet from the lamina-facet border(“V” point)

C.-I. Ju and S.-H. Kim

Fig. 11  The proximal border of the caudal pedicle can be identified by the use of a microcurette or nerve hook. Complete foraminal decompression requires full decompression of the nerve from the medial to lateral border of the caudal pedicle

the exiting nerve root. In general, epidural hemorrhage may occur frequently, and the surgical field of view may be significantly obstructed. In this case, use powdered gelatin containing thrombin (Floseal, boxter) or bipolar cauterization. Bipolar cauterization can be used to cauterize only the bleeding area accurately after confirming the bleeding point, but care must be taken to avoid cauterizing the nerve structure directly. Step 4. Perform the Foraminal Decompression and Discectomy The exiting nerve root can be retracted superiorly by a nerve hook, and discectomy and decompression are performed. The proximal border of the caudal pedicle can be identified by using a microcurette or nerve hook. Complete foraminal decompression requires full decompression of the nerve from the medial to lateral border of the caudal pedicle (Fig. 11). Once the top of the pedicle has been identified, a nerve hook can be inserted between the pedicles to assess how narrow the foramen is. Using a 2 mm Kerrison punch, remove the bone until sufficient space is created for the nerve root to be decompressed. Gently retract the nerve upwards with the nerve ring to identify disc frag-

Fig. 12  Under microscopic guidance, the nerve root is gently retracted to expose the posterior surface of the bulging or extruded disc. Remove all disc fragments compressing nerve root with a micro-pituitary rongeur

ments. Remove all disc fragments compressing nerve root with a micro-pituitary rongeur (Fig.  12). Contained disc fragments require an incision of the posterior longitudinal ligament. Curettage with reverse-angled curette is useful to remove the remaining discs that are not well-­ ­ removed with a micro-pituitary rongeur. Remove foraminal osteophytes with the use of a Kerrison rongeur.

Minimally Invasive Spinal Decompression for Cervical Spine

Step 5. Wound Closure and Postoperative Care Hemostasis with electrocautery or hemostatic foam and closure of the wound with standard layer-by-layer sutures. Wash the wound thoroughly with saline. Reapproximate the deep cervical fascia. Make one needle using a UR-6 needle and one Vicryl suture to avoid over-tightening the muscle. Close the wound with subcutaneous 4-0 Vicryl suture (Ethicon). Apply a sterile dressing. We do not routinely manage patients with a soft collar postoperatively. Patients are encouraged to perform normal range of motion without restriction.

2.2.3 Postoperative Consideration and Case Illustration Complications –– Cervical spinal instability –– Infection –– CSF leakage with or without meningitis –– New transient or permanent symptoms of nerve root dysfunction such as worsening of preexisting radiculopathy and paresthesias –– Spinal cord injury

3 Summary Cervical radiculopathy may result from compression of the nerve root due to disc herniation or degenerative stenosis with osteophyte formation in the cervical intervertebral foramen. Radiculopathy that persists despite conservative treatment requires surgical treatment and can be approached anteriorly or posteriorly using minimally invasive surgical techniques. The microscopic keyhole anterior foraminotomy via a transuncal approach represents a minimally invasive technique that allows direct removal of the compressive lesion in the neural foramen (spondylotic foraminal stenosis or extruded disc fragments) and complete decompression of the affected nerve root. Also, Posterior cervical foraminotomy allows for preserving more of the facet joint and capsule when decompressing cervical foraminal steno-

219

sis due to spondylosis. These advantages could lead to a better outcome after anterior or posterior cervical foraminotomy.

References 1. Henderson Charles M, Hennessy Robert G, Shuey Henry M, et al. Posterior-lateral foraminotomy as an exclusive operative technique for cervical radiculopathy: a review of 846 consecutively operated cases. Neurosurgery. 1983;13(5):504–12. 2. Krupp W, Schattke H, Müke R.  Clinical results of the foraminotomy as described by Frykholm for the treatment of lateral cervical disc herniation. Acta Neurochir. 1990;107(1–2):22–9. 3. Aldrich F.  Posterolateral microdiscectomy for cervical monoradiculopathy caused by posterolateral soft cervical disc sequestration. J Neurosurg. 1990;72(3):370–7. 4. Jho HD.  Microsurgical anterior cervical foraminotomy for radiculopathy: a new approach to cervical disc herniation. J Neurosurg. 1996;84:155–60. 5. Jho HD, Kim WK, Kim MH. Anterior microforaminotomy for treatment of cervical radiculopathy: part 1: disc-preserving “functional cervical disc surgery”. Neurosurgery. 2002;51:S46–53. 6. Kim SJ, Seo JS, Lee SH, Bae J.  Comparison of anterior cervical foraminotomy and posterior cervical foraminotomy for treating single level unilateral cervical radiculopathy. Spine (Phila Pa 1976). 2019;44:1339–47. 7. Liu WJ, Hu L, Chou PH, Wang JW, Kan WS.  Comparison of anterior cervical discectomy and fusion versus posterior cervical foraminotomy in the treatment of cervical radiculopathy: a systematic review. Orthop Surg. 2016;8:425–31. 8. Park YK, Moon HJ, Kwon TH, Kim JH.  Long-term outcomes following anterior foraminotomy for one or two-level cervical radiculopathy. Eur Spine J. 2013;22:1489–96. 9. Yi S, Lim JH, Choi KS, et al. Comparison of anterior cervical foraminotomy vs arthroplasty for unilateral cervical radiculopathy. Surg Neurol. 2009;71:677–80. 10. Grigorian IA, Stepanian MA, Onopchenko EV, Kadin LA, Khimochko EB, Lunina ES.  Microsurgical anterior cervical foraminotomy in spondylogenous cervical radiculopathy. Zh Vopr Neirokhir Im N N Burdenko. 2008;(2):31–5. 11. Lee JY, Lohr M, Impekoven P, et  al. Small keyhole transuncal foraminotomy for unilateral cervical radiculopathy. Acta Neurochir (Wien). 2006;148:951–8. 12. Saringer W, Nobauer I, Reddy M, Tschabitscher M, Horaczek A.  Microsurgical anterior cervical foraminotomy (uncoforaminotomy) for unilateral radiculopathy: clinical results of a new technique. Acta Neurochir (Wien). 2002;144:685–94.

220 13. Selvanathan SK, Beagrie C, Thomson S, et  al. Anterior cervical discectomy and fusion versus posterior cervical foraminotomy in the treatment of brachialgia: the Leeds spinal unit experience (2008–2013). Acta Neurochir (Wien). 2015;157:1595–600. 14. Lee DG, Park CK, Lee DC.  Clinical and radiological results of posterior cervical foraminotomy at two or three levels: a 3-year follow-up. Acta Neurochir (Wien). 2017;159:2369–77. 15. Papavero L, Kothe R.  Minimally invasive posterior cervical foraminotomy for treatment of radiculopathy: an effective, time-tested, and cost efficient motion-­ preservation technique. Oper Orthop Traumatol. 2018;30:36–45.

C.-I. Ju and S.-H. Kim 16. Ye ZY, Kong WJ, Xin ZJ, et al. Clinical observation of posterior percutaneous full-endoscopic cervical foraminotomy as a treatment for osseous foraminal stenosis. World Neurosurg. 2017;106:945–52. 17. Komp M, Oezdemir S, Hahn P, Ruetten S.  Full endoscopic posterior foraminotomy surgery for cervical disc herniations. Oper Orthop Traumatol. 2018;30:13–24. 18. Kim M, Kim HS, Oh SW, et al. Evolution of spinal endoscopic surgery. Neurospine. 2019;16:6–14. 19. Jodicke A, Daentzer D, Kastner S, Asamoto S, Boker DK.  Risk factors for outcome and complications of dorsal foraminotomy in cervical disc herniation. Surg Neurol. 2003;60:124–9; discussion 129–130.

Minimally Invasive Transforaminal Lumbar Interbody Fusion Dalsung Ryu and Jeong-Yoon Park

1 Introduction It has been two decades since Kevin Foley first reported on the muscle preservation technique for minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) in 2003 [1]. Since then, there has been an accumulation of sufficient evidence to the extent that a PubMed search retrieves more than 1000 papers related to MIS-TLIF. Currently, MIS-TLIF, along with lateral lumbar interbody fusion (LLIF), has become the standard minimally invasive fusion technique. Recent papers tend to use MIS-TLIF as a control group to compare the effectiveness of other minimally invasive fusion techniques. In addition, the majority of recent endoscopic fusion techniques, except for the Kambin triangle approach, are based on MIS-TLIF. The widespread adoption of MIS-TLIF worldwide for many years is due to its numerous advantages over conventional fusion techniques. Compared with conventional fusion techniques, MIS-TLIF is associated with superior clinical outcomes, including less blood loss,

D. Ryu Department of Neurosurgery, Inha University Hospital, Incheon, Republic of Korea J.-Y. Park (*) Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea

minimized paraspinal muscle injury, decreased pain after surgery, earlier recovery, and a shorter hospital stay [2–4]. The strongest merit of MIS-TLIF over other minimally invasive spine surgery techniques is its wide surgical indication. Similar to conventional open fusion techniques, various types of lumbar degenerative diseases can be treated with MIS-­TLIF.  The only absolute contraindication is invisible pedicles on fluoroscopy due to severe osteoporosis, degenerative change, or obesity. Vascular abnormalities and the severity of spinal canal stenosis do not limit the use of MIS-TLIF in contrast to lateral lumbar interbody fusion (LLIF) techniques [5]. No additional devices, such as neurophysiologic monitoring, are required for MIS-TLIF [6]. Although beginners may be intimidated to perform MIS-TLIF as a revision surgery for primary decompression, similar patient-reported outcomes have been reported and compared with primary MIS-TLIF [7]. Compared with the conventional transforaminal lumbar interbody fusion (TLIF) group, the MIS-­ TLIF group exhibited less intraoperative blood loss. In addition, the incidence of complications did not differ between the groups [8]. Thus, MIS-TLIF remains an effective treatment option when revision surgery is needed. According to the study by Lee et  al. [9], MIS-TLIF produced superior results compared to conventional open TLIF in terms of operation time and estimated

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_21

221

222

D. Ryu and J.-Y. Park

blood loss. Moreover, the authors reported comparable postoperative improvements in sagittal alignment between MIS-TLIF and conventional TLIF, dispelling the misconception that MISTLIF is insufficient in correcting spinal alignment. Obtaining a more lordotic angle is feasible through bilateral facetectomy, which allows for complete segment release. The correction of sagittal and coronal balance is also influenced by the placement and profile of the cage. Unlike the typical oblique placement, placing the long cage coronally and anteriorly can correct the scoliotic feature of the segment, similar to OLIF (Fig.  1). When performed by a skilled expert, the coronal placement of the cage can utilize an

angled cage to achieve sagittal correction following bilateral facetectomy. The use of an expandable cage can also aid in restoring segmental lordosis. It should be noted, however, that beginner surgeons will require a learning curve when starting with MIS-TLIF. The operative time and blood loss for MIS-TLIF tend to decrease gradually until reaching a plateau after 20–40 cases [10]. Although a longer operative time may be required during the early stages prior to reaching the asymptote, clinical outcomes remain favorable with extremely rare symptomatic complications and a similar fusion rate to open fusion [10, 11].

Fig. 1  This postoperative CT scan displays the coronal and anterior placement of the cage following minimally invasive transforaminal lumbar interbody fusion (MISTLIF), demonstrating the usefulness of this technique in

correcting the scoliotic feature of the segment in a similar manner as OLIF, as opposed to the typical oblique placement of the cage

Minimally Invasive Transforaminal Lumbar Interbody Fusion

223

2 Step-by-Step Technique

2.3 Skin Marking

2.1 Preparation for Surgery

Fluoroscopy is an essential imaging modality used in MIS-TLIF. By reviewing fluoroscopy images, the surgeon can obtain a better understanding of the three-dimensional structure of the vertebrae. The surgical table is adjusted to a slight reverse Trendelenburg position, taking into account the direction of the disc space, particularly at the L5/ S1 segment. During fluoroscopy imaging, it is crucial to obtain true anterior-posterior (AP) and lateral images to minimize any potential interference. Once the lateral scan of fluoroscopy is captured, the surgeon can mark the desired entry point for the percutaneous pedicle screw. Prior to surgery, the surgeon must identify how each vertebra is oriented cranially or caudally to set the appropriate cranial-caudal angle of fluoroscopy when inserting pedicle screws. By ensuring accurate imaging and proper orientation of the fluoroscopy machine, surgeons can successfully place pedicle screws in spinal surgery with reduced risk of complications. To ensure accurate incision placement, the surgeon first uses anteroposterior fluoroscopy to draw the midline along the spinous process. The tactile sensation of the spinous process is then used to confirm the true midline. Next, the lateral margin of the pedicle on both sides is drawn, which will serve as the incision site (Fig. 2). It is important to ensure that the incision is not too medial to the lateral pedicle line, as this could require a longer incision for screw insertion. Conversely, if the incision is too lateral to the lateral pedicle line, contralateral decompression may be difficult due to interference from paraspinal muscles. The incision should be longer than the length between the cranial and caudal pedicle screw entry points and at least 25 mm long to minimize traction injury to subcutaneous tissue.

Preoperative planning is an essential aspect of surgical intervention. The surgeon must meticulously identify the underlying lesion responsible for the patient’s chief complaint using preoperative imaging techniques. Based on a comprehensive preoperative investigation, appropriate surgical strategies must be formulated. 1. Ipsilateral decompression only or bilateral decompression. 2. Selection of the left or right approach, depending on the more symptomatic side. 3. The profile of the cage (height, length, width, and angulation). 4. The desired location of the cage (oblique or coronal placement). 5. Additional adjacent segment decompression. 6. The profile of the screw (length, diameter). 7. Optional bone cement augmentation (severe osteoporosis).

2.2 Patient Position The patient is placed in a routine prone position as typically used for lumbar spine fusion surgery. During contralateral decompression, tilting of the surgical table is required, and thus, the patient must be immobilized appropriately to prevent any potential harm. Additionally, it is important to avoid any compression of peripheral nerves or vessels. The flexible arm assembly should be attached to the table, with careful consideration given to the proper length of the arm. If the arm is too close, it may become twisted and unable to hold the tubular retractor securely. Adequate space for C-arm fluoroscopy should also be secured to ensure unrestricted switching between anterior-posterior (AP) and lateral scans. By ensuring proper patient positioning and adequate space for surgical tools and imaging equipment, surgeons can perform decompression procedures safely and efficiently.

2.4 Skin Incision and Tubular Retractor Application After sterile skin preparation, the incision is made following the skin marking. The thoracolumbar fascia is also incised sufficiently for pedicle screw fixation. Then, the muscle is dis-

D. Ryu and J.-Y. Park

224

a

b

Fig. 2 (a) Schematic comparing the approaches used with TLIF and PLIF. (b) Example of skin marking with fluoroscopy

sected gently with a finger until the lamina and facet joint are identified with touch. The first cannulated dilator is touched down to the junction of the lamina and facet joint. Serial dilators are inserted and cover the facet joint in a capped shape. Using the depth markings on the dilator, a 1 cm long tubular retractor from the skin is selected. The tubular retractor is placed over the dilators, and the flexible arm is attached to the tube and secured (Fig. 3). Then, the sequential dilators are removed. Fluoroscopy scans are recorded to confirm the surgical level. Under the microscope, soft tissue, including the facet capsule, is removed with a monopolar coagulator. The surgeon should understand where it is located under the microscope. Exposure of the inferior articular process at the medial 2/3 and the superior articular process at the lateral 1/3 is an ideal initial placement of tubular retractors. If the facet joint is severely hypertrophied or fragmented, the identification of a joint space might be difficult. Confirmation of movement by compression of the inferior articular process is an easy method to locate a joint space (Fig. 4).

Fig. 3  The tubular retractor fixed to the operating table

Minimally Invasive Transforaminal Lumbar Interbody Fusion

225

Fig. 4  After clearing the soft tissue, the joint space between the superior and inferior articular processes is confirmed. The movement around the joint is always observed with light compression of the inferior articular process

2.5 Facetectomy The inferior articular process is removed first by a drill or osteotome. A straight osteotome with a right-angle handle is required to maintain sight during hammering down (Fig.  5). Because autografts are not abundant in MISTLIF, minimal drilling is recommended only to the extent to which the osteotome is mounted. The L-shaped groove is generated little by little with an osteotome. At some point, that groove deepens, and a part of the inferior articular process is broken down (Fig. 6). However, removing broken bones is not always easy because the soft tissue around them is tight. In that case, inserting the osteotome into the grove again and twisting will separate the bone from the soft tissue. Then, it can be easily removed. The next step is to remove the superior articular process. When removing the superior articular process, pedicle injury must be avoided. The medial part of the superior articular process is removed with a Kerrison rongeur. Then, the

Fig. 5  Example of a straight osteotome with a right-angle handle (Medtronic Sofamor Danek, Memphis, TN, USA)

margin of the pedicle can be touched with a blunt hook, which is the cutting edge of the superior articular process. Cutting the superior articular process can be performed in the same way as cutting the inferior articular process with an osteotome (Fig.  7). Coagulation of bleeding from the lateral margin of the facet joint and disc space is needed.

226

D. Ryu and J.-Y. Park

a

b

Fig. 6 (a) A shallow groove is created with a drill. It will serve as a docking line for an osteotome. (b) The reversed L-shaped groove deepens with the osteotome. At some point, part of the inferior articular process will be broken and separated

Minimally Invasive Transforaminal Lumbar Interbody Fusion

227

a

b

Fig. 7 (a) The margin for superior articular process removal is palpated with the blunt hook, which is the superior border of the pedicle. (b) The tip of the superior articular process is removed with a drill. The disc space will be exposed after the removal of the superior articular process

228

2.6 Decompression of the Central Canal After total facetectomy, the far lateral part of the disc can be identified. However, the ligament flavum should be saved until the bone work is finalized because it protects the neural component during the bone work. Laminectomy is expanded cranially to the insertion of the ligament flavum. At this point, the need for contralateral decompression must be determined. If contralateral decompression is unnecessary, the next step can be skipped. For contralateral decompression, the patient is tilted to the other side. With the medial angulation of the tubular retractor following tilting of the table, the lamina and the base of the spinous process are observed (Fig. 8). Similar to facet joint removal, a groove is created with a drill, and the desired part is removed with an osteotome. With the control of angulation, the extent of removal is followed. If the patient has severe facet hypertrophy, cutting the internal portion of the contralateral facet would be a comfortable approach for decompression of the contralateral central canal. However, caution is needed because angulation that is too steep may cause spinous process fracture. At this point, the contralateral foramen is

Fig. 8  The patient is tilted to the contralateral side (Blue arrow). The medial angulation of the tubular retractor (Red arrow) will be able to obtain sufficient visualization of the contralateral nerve root

D. Ryu and J.-Y. Park

decompressed with a Kerrison rongeur. If decompression is unsuccessful, this process can be performed with an osteotome once more. All procedures can be conducted safely with the protection of the ligament flavum, which was deliberately retained. Contralateral total facetectomy from the other side is another option for contralateral decompression. However, it is not necessary once the surgeon is convinced to perform unilateral laminectomy and bilateral decompression techniques with table tilting. It is not recommended based on the basic concept of “minimally invasive surgery.” After sufficient bone work is complete, the ligament flavum is removed with a Kerrison rongeur. In particular, in patients with severe canal stenosis, the ligament flavum should be dissected from the dura to resolve the adhesion between them. The exposure should allow free fenestration of the nerve hook to ensure complete decompression of the foramen. In cases of severe canal stenosis, resection of the superior border of the lower lamina is needed. Complete decompression of both traversing and exiting nerve roots should be delayed until cage insertion because nerve root compression due to the presence of scattered bone chips occurs frequently after hammering the cage into the disc space (Fig. 9).

Minimally Invasive Transforaminal Lumbar Interbody Fusion

a

b

c

d

229

Fig. 9 (a) The lamina obstructs the field of view for contralateral decompression. (b) After extended removal of the ipsilateral lamina and the base of the spinous process, access for contralateral decompression is obtained. (c)

With the medial retractor of the thecal sac, the contralateral ligament flavum is removed with a Kerrison rongeur. (d) After complete central decompression, the thecal sac and ipsilateral traversing nerve root are visualized

2.7 Discectomy

12-mm-width spreader is inserted, and gentle rotation in a 90-degree direction will release the segment (Fig.  13). In a patient with severe osteoporosis, the cartilage should be removed ­ with a shaver or curette very carefully to prevent endplate injury. In a patient with a severely collapsed disc space where the spreader can be inserted, the osteotome should penetrate the narrow disc space under fluoroscopy guidance. In the majority of cases, the reduction of spondylolisthesis (< Grade 2) can be achieved simply with wide discectomy and distraction. As the width of the spreader increases gradually, the segment will be fully released. When approaching the anterior annulus, the piece should not be torn off, and the removed pieces should be picked up to avoid substantial vessel injury.

The table is returned to a neutral position after tilting to the other side. After the dissection of the traversing nerve root and ventral dura, venous bleeding is controlled with a bipolar coagulator. Discectomy is initiated with an incision of the disc by a scalpel while protecting the thecal sac (Fig. 10). Disc material is removed with pituitary forceps. The cartilaginous endplate is scraped off with a shaver or curette (Fig.  11). In particular, ipsilateral far lateral discectomy is performed with the retraction of the exiting nerve root (Fig.  12). This procedure is essential to release the segment and insert the desired profile of the cage. The contralateral disc is also removed as much as possible using a curette or curved pituitary forceps. When space is available, an 8- to

230

D. Ryu and J.-Y. Park

a

b

Fig. 10 (a) The disc is exposed after the medial traction of the dura. (b) The disc is incised by a scalpel with the protection of the thecal sac

Minimally Invasive Transforaminal Lumbar Interbody Fusion

a

b

Fig. 11  The cartilaginous endplate is scraped off with either shaver (a) or curette (b)

231

232

D. Ryu and J.-Y. Park

a

b

Fig. 12 (a) The disc is exposed fully to the ipsilateral side. (b) The disc is incised by a scalpel with the protection of the exiting nerve root

Minimally Invasive Transforaminal Lumbar Interbody Fusion

233

Fig. 13  The disc space is expanded with serial dilation of the spreader

2.8 Cage Insertion After sufficient removal of the nucleus pulposus and cartilaginous endplate, autograft bone chips that were obtained from laminectomy are packed into the empty disc space. If these chips are insufficient, allograft or demineralized bone matrix can be added to fill the space. Because the space is so narrow that the bony fragments may fall on the surrounding tissue, a funnel is recommended to insert them directly into the disc space (Fig. 14a). An appropriate height of the cage should be selected considering the final width of the spreader with maximal resistance, avoiding injury to the endplate. For stronger confirmation, the cage can be inserted into the disc space under fluoroscopy guidance. The selected cage is filled with bone and bone substitutes. While protecting the dura

with a root retractor, the cage is inserted into the disc space (Fig. 14b). The exiting nerve is recommended to remain unexposed until this step is complete because the simultaneous protection of both exiting and traversing nerve roots is difficult. For the coronal placement of the cage, the angled cage impactor is useful. The final location and profile of the cage are confirmed with fluoroscopy. Both exiting and traversing nerve roots are decompressed fully at this point. In ­particular, inspection of the nerve root is extremely important since compression of the exiting nerve root due to the bone chip is common. Radicular pain from the nerve compression of the undetected bone chip is one of the most common problems that requires revision surgery after MIS-­ TLIF. After meticulous bleeding control, the percutaneous pedicle screws are fixed routinely.

D. Ryu and J.-Y. Park

234

a

b

Fig. 14 (a) A funnel is used to place bone chips directly into the disc space. (b) The cage is inserted into the disc space while protecting the dura with a root retractor

3 Postoperative Consideration and Case Illustration 1. If no unusual problems occur during surgery, patients are generally able to walk while wearing a brace beginning on the day after surgery. The orthosis should be worn for approximately 1 or 2 months, according to the judgment of the attending physician. 2. Considering the implications of minimally invasive surgery, the wound is recommended to be approximated with a skin bond. A better approach is to insert the drain tube as thin as possible and then remove it quickly. 3. Radiating pain in the contralateral lower extremity has been reported to occur in 8.5% of patients after surgery, but it is mostly temporary and responds well to medical treatment [12]. If radiculopathy does not respond to conservative treatment, CT should be performed on different problems, such as hematoma or remnant bone chips. 4 . The space is relatively narrow with the restriction of tubular retractors compared with the conventional open technique, making the application of tools to protect the nerve root during cage insertion difficult. Therefore, the nerve roots must be

decompressed fully after cage insertion because soft tissue around the nerve root serves as a natural protector. The same principle holds for ligament flavum and bone work for central decompression (Fig. 15). 5. Once the dura is torn, direct repair is not comfortable due to the narrow space. Instead, the torn dura can be treated with a fibrin-collagen patch (TachoSil; Takeda Austria GmbH, Wien, Austria), fascia, fibrin glue, and other treatments (Fig.  16). If the dura is torn too extensively to be treated without direct suturing, the paraspinal incision should be extended to obtain additional space. However, symptomatic pseudo-meningocele is rare because the fascial incision is short and the potential space is confined. 6. Short-term revision due to unpredicted complications such as a postoperative hematoma or remnant bony fragment is technically demanding. Removal of the rod is required for the approach to the neural component with the application of a tubular retractor. Endoscopic decompression, either uniportal or biportal, is useful to treat this problem because it helps to obtain access to the targeted area without the impairment of instruments [13].

Minimally Invasive Transforaminal Lumbar Interbody Fusion

a

b

c

Fig. 15 A 55-year-old female complained of uncontrolled left leg pain after MIS-TLIF L4/5. The postoperative CT scan showed left L4 nerve root compression due to a remnant bone chip. (a) The bone chip was observed at

a

235

the shoulder of the left L4 nerve root. The white asterisk (*) indicates the bone chip. (b) Existing nerve root swelling is observed even after complete release with the removal of the bone chip (c)

b

Fig. 16 (a) Rootlets were extruded through the torn dura during MIS-TLIF. (b) Rootlets were reinserted into the dura, and the defect was primarily filled with gel form. (c)

4 Summary MIS-TLIF is a standard minimally invasive fusion technique that has been used to effectively treat various degenerative diseases with a wide indication. Although the learning curve is relatively steep, it is worth overcoming due to the great advantages of this technique. MIS-TLIF is expected to continue its evolution with the application of newly developed instruments and biological agents, including robots, expandable cages, and bone morphogenic proteins [14–16]. As the evidence accumulates from studies with a highly qualified comparison to endoscopic fusion, surgeons will be able to make an informed decision on which technique to use.

c

A fibrin-collagen patch (TachoSil) was applied to block CSF leakage

References 1. Foley KT, Holly LT, Schwender JD.  Minimally invasive lumbar fusion. Spine (Phila Pa 1976). 2003;28:S26–35. 2. Wu A-M, Hu Z-C, Li X-B, et  al. Comparison of minimally invasive and open transforaminal lumbar interbody fusion in the treatment of single segmental lumbar spondylolisthesis: minimum two-year follow up. Ann Transl Med. 2018;6:105. 3. Li X-C, Huang C-M, Zhong C-F, Liang R-W, Luo S-J.  Minimally invasive procedure reduces adjacent segment degeneration and disease: new benefit-based global meta-analysis. PLoS One. 2017;12:e0171546. 4. Lee MJ, Mok J, Patel P.  Transforaminal lumbar interbody fusion: traditional open versus minimally invasive techniques. J Am Acad Orthop Surg. 2017;26:124–31.

236 5. Orita S, Inage K, Sainoh T, et  al. Lower lumbar segmental arteries can intersect over the intervertebral disc in the oblique lateral interbody fusion approach with a risk for arterial injury: radiological analysis of lumbar segmental arteries by using magnetic resonance imaging. Spine (Phila Pa 1976). 2017;42:135–42. 6. Garces J, Berry JF, Valle-Giler EP, Sulaiman WAR.  Intraoperative neurophysiological monitoring for minimally invasive 1- and 2-level transforaminal lumbar interbody fusion: does it improve patient outcome? Ochsner J. 2014;14:57–61. 7. Khechen B, Haws BE, Patel DV, et al. Comparison of postoperative outcomes between primary MIS TLIF and MIS TLIF with revision decompression. Spine (Phila Pa 1976). 2019;44:150–6. 8. Wang J, Zhou Y, Zhang ZF, Li CQ, Zheng WJ, Liu J.  Minimally invasive or open transforaminal lumbar interbody fusion as revision surgery for patients previously treated by open discectomy and decompression of the lumbar spine. Eur Spine J. 2011;20:623–8. 9. Lee W-C, Park J-Y, Kim KH, et al. Minimally invasive Transforaminal lumbar interbody fusion in multilevel: comparison with conventional Transforaminal interbody fusion. World Neurosurg. 2016;85:236–43. 10. Lee JC, Jang H-D, Shin B-J. Learning curve and clinical outcomes of minimally invasive transforaminal lumbar interbody fusion: our experience in 86 consecutive cases. Spine (Phila Pa 1976). 2012;37:1548–57. 11. Park Y, Lee SB, Seok SO, Jo BW, Ha JW. Perioperative surgical complications and learning curve associ-

D. Ryu and J.-Y. Park ated with minimally invasive transforaminal lumbar interbody fusion: a single-institute experience. Clin Orthop Surg. 2015;7:91–6. 12. Yang Y, Liu Z-Y, Zhang L-M, et al. Risk factor of contralateral radiculopathy following microendoscopy-­ assisted minimally invasive transforaminal lumbar interbody fusion. Eur Spine J. 2018;27:1925–32. 13. Kim K-R, Park J-Y. The technical feasibility of unilateral Biportal endoscopic decompression for the unpredicted complication following minimally invasive transforaminal lumbar interbody fusion: case report. Neurospine. 2020;17:S154–9. 14. Lw M, Hm Z, Lr S, Azam B, Ma B, Victor C. Assessment of radiographic and clinical outcomes of an articulating expandable interbody cage in minimally invasive transforaminal lumbar interbody fusion for spondylolisthesis. Neurosurg Focus. 2020;44:E8. https://doi.org/10.3171/2017.10.FOCUS17562. 15. Price JP, Dawson JM, Schwender JD, Schellhas KP.  Clinical and radiologic comparison of minimally invasive surgery with traditional open transforaminal lumbar interbody fusion: A review of 452 patients from a single center. Clin Spine Surg. 2018;31:E121–6. 16. Chen X, Song Q, Wang K, et  al. Robot-assisted minimally invasive transforaminal lumbar interbody fusion versus open transforaminal lumbar interbody fusion: a retrospective matched-control analysis for clinical and quality-of-life outcomes. J Comp Eff Res. 2021;10:845–56.

Anterior Lumbar Interbody Fusion (ALIF) Kyeong-Sik Ryu

1 Introduction Anterior lumbar interbody fusion (ALIF) has been majorly considered as one of the surgical modalities of degenerative lumbar disc diseases [1–6]. Anterior access of the lumbar spine provides wide exposure of the entire disc space, which allows to evacuate all pathological disc material. The use of a larger cage is possible to enhance fusion success and restore disc height successfully. Particularly in the cases of lumbar intervertebral foraminal stenosis (IFS) caused by various pathologies, many reports have stated that ALIF could be effective to secure the intervertebral foraminal (IVF) height and decompress the exiting nerve root. Conventional methods of ALIF surgery would include the insertion of the graft material into the empty disc space after discectomy via anterior access and additional pedicle screws fixation via posterior approach. Anterior access of lumbar spine easily helps to remove entire pathologic disc and restores collapsed disc. If enough stabilization was achieved by one single anterior approach using stand-alone interbody cage, it could avoid the adverse effects related to additional posterior K.-S. Ryu (*) The Catholic University of Korea, Seoul St. Mary’s Hospital, Seoul, Republic of Korea e-mail: [email protected]

surgery. Postoperative pain would be minimal and short hospitalization and early return to social activity is possible.

2 History In 1906, Müller first described a transperitoneal approach to treat Pott’s disease of the sacrum [7]. However, he abandoned this procedure due to poor outcomes in subsequent patients with Pott’s disease. In 1934, Hiromu Ito noted the first known definitive ventral surgery to treat Pott’s disease of the lumbar spine [8]. He devised an extraperitoneal approach to reach the abscess cavity and performed a fusion to stabilize the spine after the abscess was resected. In 1948, Lane and Moore introduced the transperitoneal anterior fusion for the treatment of disc herniation at L3–S1 levels with extremely conservative postoperative care which recommended 1  month of laying supine position and application of a cast [9]. In 1957, Southwick and Robinson first introduced the extraperitoneal approach in lumbar spine surgery [10], and Harmon in 1960 [11]. Harmon’s extraperitoneal technique to treat spondylolisthesis and degenerative disc disease. In 1969, Dwyer did the first instance of anterior instrumentation to correct thoracolumbar scoliosis with the use of titanium cables placed through vertebral body screws [12].

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_22

237

238

K.-S. Ryu

In 1991, Obenchain reported the use of laparoscopic techniques for transperitoneal ALIF [13]. Following the introduction of these innovative techniques, several authors applied lumbar interbody fusion surgery. However, Longer operation times, steep learning curves, and low fusion success rate made the laparoscopic approach abandoned. In 1997, Mayer proposed mini-open muscle splitting access to the retroperitoneal space. The mini-open approach made open surgery faster and less traumatic than before [14]. This approach then involves an anterior approach to the retroperitoneal space where the bifurcations of the great vessels are carefully visualized before exposing the L5–S1 or L4–L5 disc spaces. Fig. 1  Three-dimensional CT abdominal angiography.

3 Indications and Contraindications Indications can be degenerative disc disease, grade I spondylolisthesis, symptomatic pseudoarthrosis, lumbar foraminal stenosis, trauma, deformities, and infectious or tumorous conditions. Contraindications include prior abdominal surgery, solitary kidney on the side of exposure, spinal infection, and high-grade spondylolisthesis.

4 Surgical Technique Anterior surgical access to the lumbar spine crosses the abdominal cavity through a retroperitoneal or transperitoneal route. Therefore, the patient should be prepared similar to abdominal surgery such as bowel preparations and giving purgatives to empty the gastrointestinal system. The body surface is shaved from the mamillae to the symphysis. Whether to approach left or right is determined by referring to the shape and shape of the large blood vessels in the abdomen in the anterior part of the intervertebral disc is observed in 3D CT angiography before surgery (Fig.  1). If 3D CT angiography is not useful, MR images can also be used to observe the condition of blood vessels in the abdomen (Fig. 2). In particular, the

Fig. 2  T1 axial lumbar MRI (a) abdominal major vein, (b) retroperitoneal fat

thickness of the retroperitoneal fat layer can be confirmed with the MR image, so dissection for exposing the anterior intervertebral disc can be helpful at work. During general anesthesia, intraoperative venous line and an arterial line for continuous arterial. A Foley catheter is introduced into the bladder for intraoperative the bladder. Pulse oximetry should also be performed at big toe to monitor for ischemia from temporary arterial compression while the common iliac artery is being retracted.

Anterior Lumbar Interbody Fusion (ALIF)

239

Fig. 3  “Da Vinci” position

First assistant

Surgeon

The patient is placed in the supine position. “Da Vinci” position (Fig.  3) or standard supine with the legs closed can be used. Localization for the target level is made with a portable X-ray or C-arm fluoroscope. Especially, the orientation of the L5/S1 disc space is marked as it projects onto the skin fluoroscopic view (“disc line”). The anterior border of the promontory is also marked on skin (“border line”). A transverse line is drawn from this intersection point onto men. The transverse line, called the “corridor line,” is located in the middle distance between the umbilicus and the symphysis (Fig. 4).

Fig. 4  Disc line and border line on fluoroscopic view

K.-S. Ryu

240

5 Retroperitoneal Approach Vertical and midline skin incision is usually used but, for the L5/S1 exposure, a transverse incision can be performed between the umbilicus and the symphysis pubis. After dissection of skin and soft tissue, the rectus fascial sheet has been exposed. If target level is L5–S1, the linea alba is split in the midline and the peritoneum is exposed. If target levels are above L5–S1, the rectus muscle is completely mobilized from medial to left lateral and the posterior rectus sheath is exposed. The posterior rectus sheath can then be split longitudinally starting from the arcuate line (Fig.  5). The peritoneum is carefully and bluntly detached from the inner abdominal side. Any lesions of the peritoneum should be closed immediately before dissection is continued. Care must be taken not to injure the genitofemoral nerve, which crosses on the medial surface of the psoas muscle (Fig. 6). The psoas muscle and the common iliac vessels with the ureter are identified. Arterial structures are easily retraced. But, venous structures should be retracted very gently because they have a thin wall and are easily injured. At L5–S1 level,

Fig. 6  Direction for dissection in retroperitoneal approach

the superior hypogastric plexus is located at the front of the disc. The superior hypogastric plexus must be carefully pushed medially with avoiding any kind of coagulation for preventing retrograde ejaculation postoperatively. Sometimes segmental vessels need to be ligated for the exposure of the target area. The venous branches need meticulous preparation. When vascular injury happens, careful bleeding control is required. Uncontrolled major vessel injury should be managed by vascular surgeon.

Fig. 5  Arcuate line

Anterior Lumbar Interbody Fusion (ALIF)

6 Transperitoneal Approach This approach is an alternative for patients who have had conventional abdominal surgery, and in patients receiving revision spinal surgery. Very obese patients are also indicated. The peritoneum is split in the midline and armed with temporary sutures. The abdominal contents are gently pushed away from the anterior part of lumbar spine with abdominal towels. The mesenterium and small intestines are mobilized and pushed into the right upper quadrant of the abdominal cavity. The sigmoid colon and mesocolon are pushed into the left lower quadrant and retracted with blunt Langenbeck hooks. Once direct visualization of the target disc is obtained by proper retraction of retractors [Steinman pins or Hohmann retractor (Fig.  7)], an annulotomy from lateral to medical direction is performed. Radical discectomy is done by disc removal with a piecemeal approach using a pituitary rongeur. Preservation of bony endplate is mandatory for successful fusion. A microscope can be used for further disc removal of sequestered fragments in the canal to complete the decompression. Various graft materials can be used such as autograft from the iliac crest, allograft, synthetic material, PEEK, or metal cage. If a stand-alone cage is available, it can make the surgery to be performed only with anterior access. a

b

241

Prior to the disc prosthesis implant, a trial prosthesis is inserted to select for proper implant fit. Using C-arm fluoroscope, confirming depth, position, and lordosis of index level is determined. The appropriate implant is chosen and finally implanted. Following meticulous hemostasis, drain is used, if excessive bleeding from the intervertebral space is noted. The posterior layer of the rectus sheath is closed to reduce the risk of herniation. Standard subcutaneous and skin closure is routine. The patient is recommended to stand up with a back brace for 24 h after surgery, get up in bed, and go to the bathroom. A wide range of back motion is prohibited over the first 4 weeks. After this early stage, a more intensive rehabilitation program may be needed (Fig. 8).

Fig. 7  Exposure of target disc using Hohmann retractor

c

d

Fig. 8  A 67-years old male presenting L4–5 and L5–S1 degenerative spondylolisthesis with foraminal stenosis (a, b). After two level ALIF with stand-alone cage (c), enough reduction of foramen of target levels are noted (d)

K.-S. Ryu

242

7 Complications

References

There are significant risks inherent in the ALIF approach. The procedure is performed in the immediate vicinity of the large blood vessels that connect to the legs. Damage to these large blood vessels can cause excessive blood loss. For men, another risk specific to this approach is the risk of superior hypogastric plexus causing a condition called retrograde ejaculation when injured approaching the disc space of L5–S1 level. The superior hypogastric plexus can cease functioning, and without this coordinated innervation of the valve, ejaculatory fluid follows the least resistant route to the bladder. This complication does not cause impotence because these nerves do not control erections. Retrograde ejaculation occurs in less than 1% of cases and tends to resolve over time. Fusion failure, incisional hernia, ureter injury, sympathetic chain injury, and complications related to implants such as pesudoarthrosis or migration of implant are also noted.

1. Crock HV. Anterior lumbar interbody fusion: indications for its use and notes on surgical technique. Clin Orthop Relat Res. 1982;165:157–63. 2. Cyriac M, et  al. Anterior lumbar interbody fusion with cement augmentation without posterior fixation to treat isthmic spondylolisthesis in an Osteopenic patient-a surgical technique. Int J Spine Surg. 2018;12(3):322–7. 3. Duan P, et al. Anterior lumbar interbody fusion (ALIF): technique video: 2-dimensional operative video. Oper Neurosurg (Hagerstown). 2020;19(4):E404. 4. Malham GM, Wagner TP, Claydon MH.  Anterior lumbar interbody fusion in a lateral decubitus position: technique and outcomes in obese patients. J Spine Surg. 2019;5(4):433–42. 5. Mobbs RJ, et  al. Anterior lumbar interbody fusion as a salvage technique for Pseudarthrosis following posterior lumbar fusion surgery. Global Spine J. 2016;6(1):14–20. 6. Richter M, Weidenfeld M, Uckmann FP.  Anterior lumbar interbody fusion. Indications, technique, advantages and disadvantages. Orthopade. 2015;44(2):154–61. 7. Debeyre J, De Seze S, Levitan G.  Direct surgical approach to the lumbosacral foci of Pott's disease by the transperitoneal route. Presse Med (1893). 1955;63(86):1828–30. 8. Ito H, Tsuchiya J, Asami G. A new radical operation for Pott's disease. J Bone Joint Surg. 1934;16:499–515. 9. Lane JD Jr, Moore ES Jr. Transperitoneal approach to the intervertebral disc in the lumbar area. Ann Surg. 1948;127(3):537–51. 10. Southwick WO, Robinson RA.  Surgical approaches to the vertebral bodies in the cervical and lumbar regions. J Bone Joint Surg Am. 1957;39-A(3):631–44. 11. Harmon PH.  Anterior extraperitoneal lumbar disc excision and vertebral body fusion. Clin Orthop. 1960;18:169–98. 12. Dwyer AF, Newton NC, Sherwood AA.  An anterior approach to scoliosis. A preliminary report. Clin Orthop Relat Res. 1969;62:192–202. 13. Obenchain TG.  Laparoscopic lumbar discectomy: case report. J Laparoendosc Surg. 1991;1(3):145–9. 14. Mayer HM.  A new microsurgical technique for minimally invasive anterior lumbar interbody fusion. Spine (Phila Pa 1976). 1997;22(6):691–9. discussion 700

8 Summary ALIF involves approaching the lumbar spine anteriorly through abdomen to remove the target disc and then fusing it with bone graft or bone graft substitute. Anterior access of the lumbar spine provides wide exposure of the entire disc space, which allows to evacuate all pathological disc material. The use of a larger cage is possible to enhance fusion success and restore disc height successfully. However, its surgical anatomy is not familiar to spine surgeon, and there are risks of serious complications such as major abdominal vessels injury. Sufficient knowledge and caution about each surgical step during surgery are mandatory.

Oblique Lumbar Interbody Fusion (OLIF) Dongwuk Son and Suhun Lee

1 Introduction The process of OLIF involves approaching the disc through the anterior aspect of the psoas muscle, first described by Michael Mayer in 1997. OLIF has become the most preferred technique owing to its minimal invasiveness and short learning curve to master the technique. Compared to the posterior approach fusion, OLIF preserves the posterior structures, such as the lamina, facet joint, and posterior ligament, resulting in relatively quicker recoveries. Additionally, without direct decompression, using a large-sized cage can increase the height of the intervertebral disc and neural foramen, resulting in improved symptoms. OLIF and trans-psoas lateral interbody fusion (direct lateral interbody fusion: DLIF) are similar

surgical processes. However, OLIFs do not require monitoring because of the anterior approach to the psoas muscle. OLIFs can be performed on the L5/S1 by approaching the anterior space of the iliac crest. However, retroperitoneal dissections are necessary, often unfamiliar to spinal surgeons, resulting in the possibility of great vessel and ureter injuries compared to that during the posterior approach. Therefore, sufficient knowledge about the surgical procedure and complications is key. In this chapter, the preoperative planning, surgical procedures, and the intraoperative complications of the “anterior to psoas approach” (ATP: L2–5) and “between the iliac bifurcation” (BIB: L5–S1) approach will be described in detail (Fig. 1).

D. Son · S. Lee (*) Department of Neurosurgery, Pusan National University Yangsan Hospital, Yangsan-si, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_23

243

D. Son and S. Lee

244

Inappropriate for indirect decompression: an extruded herniated disc, calcified disc or posterior osteophyte, severe central canal stenosis (resting pain), severe facet hypertrophy, or fused facet.

2.3 Contraindications Abdominal aortic dissections or aneurysms. Spondylolisthesis exceeding Grade III. Local infectious spondylitis.

3 Step-by-Step Technique 3.1 OLIF L2–5 (Anterior to Psoas Approach) [1–3] 3.1.1 Preoperative Plan Main Procedure: The anatomical locations of the relevant structures encountered during surgery (bony pelvis*, 10th–12th rib*, great vessel†, and left ureter‡) should be checked using a preoperative L-spine X-ray and computed tomography (CT) images. Fig. 1  The two approaches frequently used in OLIFs. ATP: anterior to psoas approach (L2–5), BIB: between iliac bifurcation approach (L5–S1)

2 Indications and Contraindications 2.1 Indications –– Radiological: spinal stenosis with segmental instability and spondylolisthesis. –– Clinical: Pain and claudication that is refractory to conservative treatment.

2.2 Relative Contraindication History of transperitoneal or retroperitoneal surgery. History of abdominal radiation therapy. Previous ALIF/OLIF surgery. L5/S1: Young male (retrograde ejaculation).

* The anatomy of the pelvis and rib: • The pelvis shape is a crucial factor for orthogonal maneuvers. When the anterior superior iliac spine of the ilium (ASIS) is high and protrudes anteriorly, orthogonal cage insertion can become difficult or impossible. • The ribs also present as obstructive structures for OLIF. In L2/3 (in most cases) or L3/4 (in some cases), the ribs may extend down to the disc space, making it difficult to insert the cage parallel to the disc space. A preoperative L-spine lateral bending X-ray is effective for the prediction of the accessibility through the jack-knife position.

† The location of the IVC and iliac vein: • Visualization of the IVC and iliac veins is rare during the left-side ATP approach. However, the preoperative CT should be thoroughly assessed to confirm any abnormalities in the

Oblique Lumbar Interbody Fusion (OLIF)

245

vessels. Specifically, for the L4/5 approach, the left iliac vein could run close to the L5 upper endplate, resulting in increased possibilities of injury during disc space exposure. (Fig. 2).

enhanced CTs (arterial phase, ureter phase), mainly performed in urology, may help in confirming the location of the ureter for beginners. (Fig. 3). • The ureter location can be classified into three ‡ Location of the ureter: categories. 1) in the retroperitoneal fat, 2) on • The ureter location is difficult to confirm using the psoas muscle, and 3) beside the medial only a non-enhanced CT image or artery phase border of the psoas muscle (Fig. 4). The ureter enhanced CT image. Dual-phase contrast-­ is not identifiable during the retroperitoneal Fig. 2  Preoperative CT/ MR scans are used to check the vessel anatomies: The left iliac vein (blue color) runs close to the L4/5-disc space, making the ATP approach impossible.

Fig. 3  A dual-phase CT scan. In the arterial phase, the position of the ureter cannot be accurately assessed. However, in the ureter phase, the ureter is contrast-enhanced and thus correctly assessed

246

D. Son and S. Lee

Fig. 4  Location of Ureter. (Red circle) on the psoas, (Blue circle) in the retroperitoneal fat, and (Yellow circle) beside the medial border of the psoas muscle

Fig. 5  The compressive area in the right decubitus position

approach if the left ureter is located in the retroperitoneal fat. When the left ureter is located on the psoas muscle, it is easily identifiable and medially dissected. However, if the ureter is located beside the medial border of the psoas muscle, ureter injuries are highly possible. In this case, the ureter is not identified and is hidden in the peri-vertebral fat pad even when retroperitoneal dissections are performed at the anterior margin of the psoas muscle.

3.1.2 Position Main Procedure: The patient typically has the right lateral decubitus position* with a slightly flexed left hip†. A soft pillow is applied to the right compression site (right ear, right axilla, bilateral elbow, right hip, bilateral knee‡, right ankle) (Fig.  5). Using the C-arm lateral image, the patient’s decubitus posture is adjusted to ensure no tilt one side, and the position is fixed using side rest and taping on the chest and pelvis.

Oblique Lumbar Interbody Fusion (OLIF)

• Tip 1. Jack-knife position –– The jack-knife position has the following advantages: skin tightening, rib elevation, and ease of access in patients with approach-side concave scoliosis. However, an extreme jack-knife position increases the risk of psoas paresis [4]. The jackknife position may also cause contralateral endplate injuries during OLIF cage insertion. *The right lateral decubitus position is preferable because of the vein position. † Hip flexion is also important for psoas muscle relaxation. Insufficient hip flexion may cause difficulties in psoas mobilization. ‡ The peroneal nerve runs to the lateral knee area. In the right decubitus position, the lateral side of the right knee is particularly vulnerable to compression, resulting in an increased risk of postoperative peroneal palsy.

3.1.3 Skin Incision Main Procedure: The Trendelenburg of the table is adjusted to obtain a true lateral image from the C-arm. The disc levels and anterior margin of the vertebral body is marked. A skin incision is designed differently according to single level, double level, and multilevel. An incision line is made on two fingers (5 cm) anterior to the vertebral body or ASIS. (Fig. 6). a

b

247

Tip 1. Single level: For the L4/5, the disc level is marked corresponding to the lower endplate of L4 and the upper endplate of L5, followed by marking the anterior margin of the L4 and L5 vertebra bodies. The incision is made approximately 3–5 cm (2 fingers) anterior to the margin of the vertebra body or ASIS*. An incision length of 5–6 cm is sufficient for the OLIF approach (Fig. 6b). Tip 2. Double levels: In the cases of L3/4/5, an incision is made corresponding to the L3/4-­ disc space and L4/5-disc space. Like the single level, a 5–6  cm incision is sufficient to access the double level through the so-called sliding window (Fig. 6c). Tip 3. Multilevel: For more than 2 levels, a separate incision is used, or a longer single incision is designed, followed by a separate incision at the muscle layer (Fig. 6d). Tip 4. Close to the rib: In the cases of L3/4, approaching through the jack-knife position is often possible (Fig.  7). However, in some patients with short waists, the L3/4 approach or the L2/3 approach requires an intercostal approach between the ribs 10/11. (Fig. 6d). *Reasons for two-finger anterior incisions from the vertebral body or the ASIS: 1) a relatively safe area for the superficial nerve (iliohypogastric and ilioinguinal nerve), 2) In the cases of DLIF incisions, the visual field of the anterior part of the psoas muscle is difficult to secure. c

d

Fig. 6  The skin incision design: (a) two fingers anterior from the ASIS, (b) single-level incision for L4/5, (c) double-­ level incision for L3/4/5, (d) multilevel incision for L1/2/3/4/5, the blue circle indicates the 11th and 12th rib

248

D. Son and S. Lee

Fig. 7  The jack-knife position for rib elevation. In the flat position, L2/3 cannot be accessed because of the rib obstruction, but it can be accessed by the Jack-knife position

3.1.4 Abdominal Muscle Dissection Main Procedure: After making a skin incision and below the subcutaneous fat, three layers of abdominal muscle can be observed. Each muscle should be dissected parallel to the direction of every muscle bundle. Fat and loose connective tissues are identified between each layer. After the dissection of the transverse abdominis muscle, a thin membrane called the transverse fascia is exposed. Retroperitoneal fat is identified below the transverse fascia (Fig. 8).

Tip 2. The transverse abdominis muscle, a thin layer muscle, requires attention during the dissection. A risk of peritoneum injury persists, especially in lean patients, in the anterior area of the transverse muscle. When dissecting this area, the transverse fascia must be secured by splitting the muscle using a double dissector rather than a bovie coagulator for safety. Tip 3. The abdominal superficial nerve (iliohypogastric nerve and ilioinguinal nerve) runs between the internal oblique muscle and the Tip 1. During the muscle dissection, muscle cuttransverse abdominis muscle (Fig. 8f). When ting using a bovie or sharp dissections should the superficial nerve runs in the op field, it can be minimized. Muscle splitting using double-­ be retracted to the cephalic or caudal direction handed dissectors could prevent abdominal after dissection of the lower fat pad of the muscle damage. nerve.

Oblique Lumbar Interbody Fusion (OLIF)

249

a

b

c

d

e

f

Fig. 8  Abdominal wall dissection. (a–c) The three layers of abdominal muscle. The dissection of each muscle must be performed parallel to the direction of each muscle bundle (white arrow). (d) After the dissection of the transverse abdominis muscle, the transverse fascia is exposed. (e) Retroperitoneal fat is identified below the transverse

fascia. (f) A schematic illustration of the abdominal wall muscle and abdominal superficial nerve. The Iliohypogastric nerve and Ilioinguinal nerve run between the transverse and internal oblique muscles. T transverse abdominis muscle, I internal oblique muscle, E external oblique muscle

3.1.5 Retroperitoneal Approach Main Procedure: After a blunt dissection is performed in the cephalic-caudal direction between the abdominal wall and retroperitoneal fat, the psoas muscle can be palpated. The fat tissue covering the psoas muscle requires additional blunt dissection from the dorsal to ventral to confirm the psoas fascia. The genitofemoral nerve (GFN) running inside the psoas fascia and the ureter running in the retroperitoneal fat are checked. When the dissection is performed medially along the psoas fascia plane, the anterior margin of the psoas muscle is confirmed (Fig. 9).

Tip 1. If the retroperitoneal fat obscures the field of view, additional dissection of the fat tissue attached to the abdominal wall in the cephalic and caudal directions is required. It reduces the intrusion of fat into the operation field. Tip 2. Approaching the retroperitoneal fat too far dorsally is not necessary. Just touching the psoas muscle is sufficient. An excessively dorsal approach leads to the transverse process and may damage the cutaneous nerve and result in bleeding in the blind area.

D. Son and S. Lee

250 Fig. 9 Retroperitoneal approach. (a) Blunt dissection in the cephalic-caudal direction between the abdominal wall and retroperitoneal fat. (b) The fat tissue covering the psoas muscle requires additional blunt dissection from the dorsal to ventral direction. (c) The genitofemoral nerve (GFN) running inside the psoas fascia must be checked, and further blunt dissection to the anterior margin of the psoas muscle performed accordingly. (d, e, f) Schema of the axial plane and the blunt dissection process

a

d

b

e

c

f

3.1.6 Psoas Muscle Retraction Main Procedure: At the medial border of the psoas muscle, a thin membrane* can be found, covering between the peri-vertebral membrane and psoas muscle fascia. This thin membrane can be opened using a double-ended dissector, and the psoas muscle bundle can be found. The loose connective tissue between the psoas muscle and annulus is

retracted dorsally using peanut cotton. At this time, the psoas muscle is retracted sufficiently to allow the trial entrance (Fig.  10). In these processes, the location of the important anatomical structures, such as the genitofemoral nerve, lumbar sympathetic nerve (SN)†, ureter‡, and segmental artery or vein§, usually hidden inside the retroperitoneal fat, should be recognized (Fig. 11).

Oblique Lumbar Interbody Fusion (OLIF)

251

a

b

c

d

Fig. 10  Psoas muscle retraction. (a) A thin membrane covering the psoas muscle, called the psoas fascia, is connected to the anterior fat of the vertebral body. At this time, the bundle of the psoas muscle has not been identified. (b) Opening this thin membrane with a double-ended dissec-

Genitofemoral nerve Segmental artery

Sympathetic chain

Fig. 11  The location of the genitofemoral nerve, lumbar sympathetic nerve, ureter, and segmental artery/vein

tor reveals the psoas muscle bundle. (c, d) If the ureter is identified during psoas muscle retraction, it is medially retracted. The dissection of the space between the psoas muscle fiber and annulus and the psoas muscle retracted dorsally. The yellow dotted line represents the ureter

*If the psoas fascia is not opened, the psoas muscle is not retracted but only wedged at the anterior margin of the psoas muscle. If the psoas muscle is retracted with excessive force in these cases, resulting in an increased risk of GFN damage or psoas paresis. † The pathway of SN: The SN enters the abdominal cavity at the L2/3 level and is beside the anterior margin of the psoas muscle. It subsequently travels towards both the caudal and medial direction between the aorta and psoas muscles [5–7]. If the SN is located within the range of the annulotomy, SN is dissected, followed by medial retraction. ‡ Ureter injuries: When the left ureter is in the retroperitoneal fat or on the psoas muscle (Fig. 4), it is usually on the medial side of the retractor. However, when the ureter is located

D. Son and S. Lee

252

a

b

c

Fig. 12  Placement of the retractor. (a) C-arm AP image: the retractor in a direction parallel to the disc, (b) C-arm lateral image: the retractor is positioned in the middle

third of the cephalad vertebra body, (c) Mispositioning of the retractor pin

on the anterior margin of the psoas muscle, it is not medial to the retractor. The ureter positioned below the psoas muscle or undissected retroperitoneal fat could be damaged during the retractor pinning process.

inside the retroperitoneal fat, and can ­consequently be kinked or directly injured by pin insertions. –– When the insertion point of the pin is relatively dorsal, attention must be paid to the orthogonal insertion. If the orthogonal maneuver is insufficient, the pin could potentially penetrate the posterior wall and cause thecal sac injuries (Fig. 12c). • Tip 2. Retractors are not essential. There is an increased risk of endplate damage if the installed retractor is not parallel to the disc level by the rib or iliac bone. In this case, manual retraction of the psoas muscle without the installation of a retractor is beneficial for performing the disc parallel maneuver.

§ Location of segmental vessels: Since the segmental artery runs closer to the caudal vertebra at the disc level, it is safe for pinning the cephalad vertebra. However, a segmental artery injury can occur when pinning at or above the mid-height of the cephalad vertebra body.

3.1.7 Retractor Placement Main procedure: The retractor applying site is properly exposed from the psoas muscle and retroperitoneal fat. It is important to install the retractor in a direction parallel to the disc using the C-arm AP image. In the C-arm lateral image, the retractor is positioned in the middle third of the vertebra body. When the location of the retractor is well selected, the retractor fixing pin is installed to the cephalad vertebra. (Fig. 12). • Tip 1. Attention should be paid to the following points to prevent possible major complications during the retractor fixing pin installation process: –– Insertion of a pin over a muscle where retroperitoneal fat remains involves a risk. A ureter located beside the medial border of the psoas muscle (Fig. 4) may be concealed

3.1.8 Annulotomy and Discectomy Main procedure: The required position for annulotomy varies depending on the objectives of the operation and the possibility of orthogonal maneuver. Using a C-arm true lateral image, the annulotomy anterior and posterior margins must be checked with a double dissector. An annulotomy of a sufficiently large square shape reduces the risk of “flapper valve”*. After annulotomy, discectomies are performed using sequential shavers and pituitary forceps (Fig. 13a). • Tip 1. Endplate injuries often occur when using shavers. A shaver should be used parallel to the disc space with C-arm guidance.

Oblique Lumbar Interbody Fusion (OLIF)

253

Attempts to increase the disc height or excessive discectomies through large-size shavers are major causes of endplate fractures. Additional disc height restorations are possible through contralateral annulotomy followed by trial insertions. • Tip 2. Positioning the Annulotomy

compared to trial size. The appendage of the annulus interferes with the trial insertion into the disc space. Even if the trial enters disc space, it pops out when the insertion pressure is removed. Increased pressure is necessary for the insertion trial, resulting in an increased risk of endplate injuries at the insertion site.

–– Relative anterior site annulotomy: it is advantageous for securing lordosis but has a lesser indirect decompression effect. If we cannot provide an adequate orthogonal angle by iliac crest, an annulotomy should be started anteriorly to prevent contralateral root injuries. However, relative ­anterior annulotomy also has an increased risk of sympathetic chain injuries or unintended ALL injuries. –– Relative posterior site annulotomy: This provides the advantage of increased indirect decompression effect but has the disadvantage of obtaining a relatively small lordosis angle. However, posterior annulotomy requires increased psoas muscle retraction in addition to an increased risk of psoas paresis. Additionally, annulotomy performed posteriorly with inadequate orthogonal angles is associated with increased risks of contralateral nerve root injuries by cage (Fig. 14). *The “flapper valve” phenomenon occurs in cases of small or not rectangular annulotomy

3.1.9 Contralateral Annulus Release Main procedure: Contralateral annulus release is required to place a cage on the bilateral epiphyseal ring. If the contralateral annulus is not released, the trial cannot advance deeply and consequently pops out. By entering the Cobb’s elevator parallel to the disc space, it will stop on the opposite side annulus. Under the C-arm guide, the Cobb elevator is carefully advanced deeper using a mallet, and the sudden loss of insertion tension can be felt when the contralateral annulus is released. This process is performed according to both the upper and lower endplate (Fig. 13b). Tip 1. If the Cobb’s elevator enters the opposite side deeply, it can damage the opposite side psoas muscle, the IVC, or right iliac vein. Especially at the L2/3 level, the risk of kidney injuries or renal artery/vein injuries increases.

c a

d

b

e

Fig. 13  C-arm images of sequential procedures (a) sufficient discectomy using a shaver, (b) contra-lateral annulus release using a long Cobb’s elevator, (c) selection of cage

width and height with sequential cage trial, (d) endplate preparation using a rasps or curette, (e) cage insertion to maintain orthogonal maneuver and parallel to disc space

D. Son and S. Lee

254

Fig. 14  Illustrative case of insufficient orthogonal angle. The relatively anterior annulotomy could reduce the risk of contralateral root injuries

a

b

Fig. 15  Orthogonal maneuver. (a) After the trial is partially anchored in the disc space, (b) the direction is changed orthogonally, and the trial is inserted

3.1.10 Sequential Trial Size Selection Main procedure: The trial is partially anchored in the disc space along the retroperitoneal corridor and subsequently adjusted in the direction parallel to the disc space in the C-arm AP image (Fig. 13c). The direction is then changed orthogonally and additionally inserted (Fig.  15) followed by the distraction of the disc space by

sequentially increasing the trial size. A trial size with sufficient resistance to the manual pull-out test should be selected. • Tip 1. An inadequate discectomy results in increased resistance during trial insertion. Inserting the trial with excessive force results in the remaining disc potentially exiting the

Oblique Lumbar Interbody Fusion (OLIF) Fig. 16 (a) Illustrative case of insufficient orthogonal angle with narrow annulotomy corridor. (b) The relatively short length and less width cage could reduce the risk of contralateral root injuries

a

contralateral annulus and causing contralateral root compressions. If the pressure is high in trial use, the sufficiency of both the annulotomy and the discectomy should be assessed. • Tip 2. Cage height selection –– Relatively large height cage: the effectiveness of indirect decompression can be increased. However, there is a risk of endplate injuries and vertebral body fractures (especially in osteoporosis patients). Even in the absence of radiological problems, severe postoperative back pain can be occurred due to the over distraction of the facet joint capsule. –– Relatively small height cage: In addition to failed indirect decompression, cage migration may also occur during position changes or the follow-up period. When selecting the cage height, it is necessary to check sufficient pressure by performing manual pull-out tests. • Tip 3. Cage width, length selection –– Considering the subsidence, placing the cage on the bilateral diaphysis is preferable, for which cages with large widths and lengths are preferred. However, when the orthogonal is insufficient, the use of cages with a large width or a large length may result in contralateral root injuries. In such cases, the use of smaller cages is recommended (Fig. 16).

255

b

3.1.11 Endplate Preparation and Cage Insertion Main procedure: The remnant disc and cartilaginous endplate are removed using a rasp or curette (Fig. 13d). Subsequently, the retroperitoneal and disc spaces are irrigated with saline. After connecting the cage to the inserter, the inside of the cage is filled with DBM. The cage is advanced parallel to the disc space and orthogonal to the mid-disc space (Fig.  13e). After disconnecting the cage from the inserter, the inserter is removed using a slap hammer. The cage can potentially be pulled out in this process. The position of the cage must be thoroughly checked once more on the C-arm image after removing the inserter. Tip 1. The inserter sleeve prevents DBM from leaking out from the cage and could also prevent endplate injuries due to the cage footprint. However, caution is essential when the sleeve enters deeply into the opposite side and causes damage to the opposite structure during cage insertion.

3.1.12 Closure Main procedure: Hemostasis is done using coagulation or bone wax at the pin removal site. After repositioning the retroperitoneal fat, layer-by-­ layer closure of the three-layer muscle and subcutaneous is performed.

D. Son and S. Lee

256 Fig. 17  The different approaches according to the location of the iliac vein. (a) Sufficient space between the bilateral iliac veins is permissive to the BIB approach. (b) The iliac vein present at the mid-line of the disc making the BIB approach impossible. However, the ATP approach is possible

a

b

Fig. 18  Classification of the location of the LIV. (Type I) LIV runs laterally for more than two-thirds of the length of the left side L5–S1 disc or is alternately located in a floating position; (type II) LIV is located medially within two-thirds

of the length of the left side of the L5–S1disc, but the perivascular adipose tissue under the LIV (arrow); (type III) no perivascular adipose tissue was seen under the LIV. Adapted from the Chung NS European Spine Journal (2017)

Tip 1. The muscle approximation requires attention because the abdominal muscles do not have fascia. If the suture is pulled excessively, a defect may occur in another area, which may lead to an incisional hernia. Care must be taken not to entrap the superficial nerve during muscle closure.

half, making the BIB approach possible in more than 60% of cases. However, in practice, BIB access may not be possible depending on the course of the left iliac vein and the absence of a fat pad below the left iliac vein. This needs thorough preoperative evaluation. –– In the case of the L5/S1 transitional vertebra, the IVC confluence location is often not accessible using the BIB approach, but anterior to psoas approach can be considered on a case-by-case basis (Fig. 17). • Tip 2. Fat pad of iliac vein –– If the left iliac vein is near the border of the annulotomy, dissection and lateral r etraction of the left iliac vein is ­ required. If there is a fat pad below the iliac vein, dissection is easily possible. However, if there is no fat pad, the risk of iliac vein injury during dissection is high. Thus, preoperative imaging is key for confirming the presence of the fat pad (Fig. 18).

3.2 OLIF L5–S1 (Between the Iliac Bifurcation Approach: BIB Approach) [8–10] 3.2.1 Preoperative Plan Main Procedure: The location of the great vessels should be confirmed preoperatively using a CT L-spine. A posterior approach is recommended in cases with insufficient space between the iliac veins or difficult mobilization of the veins. • Tip 1. Location of the iliac vein [11] –– The location of the IVC confluence is 63% above the L5 half and 37% below the L5

Oblique Lumbar Interbody Fusion (OLIF)

a

Fig. 19  The angle differences in the C-arm for taking true AP images according to the L3/4 L5/S1 disc level. (a) L3/4 level true AP image: The disc space of L5/S1 is not

257

b

visible, (b) L5/S1 level true AP image: Disc space of L5/ S1 and both endplates are visible

Fig. 20  The skin incision design for the BIB approach: A perpendicular line is drawn from the center point of the L5/ S1 disc space ventrally. A parallel extension line of the S1 upper endplate is drawn. Afterward, an incision line connecting the two extension lines on the two fingers anterior part of the ASIS is drawn

3.2.2 Position Main Procedure: The position of the BIB approach and the ATP approach are the same. Tip 1. The inclination of L5/S1 disc is high compared to other levels. In that regard, it is necessary to check the angle at which the true AP image is obtained with the C-arm preoperatively, and the area of the drape and location of scrub nurse should be adjusted accordingly (Fig. 19).

3.2.3 Skin Incision Main Procedure: The disc space of L5/S1 and the vertebrae anterior margins of L5 and S1 are marked. A perpendicular line is drawn from the center point of the disc space in the ventral direction. A parallel extension line of the S1 upper endplate is drawn. Afterward, an incision line is drawn connecting the two extension lines on the two fingers long anterior part of the ASIS (Fig. 20).

D. Son and S. Lee

258

a

b

c

d

e

f

Fig. 21  The dissection of the abdominal wall; (a) Exposed aponeurosis of the external oblique muscle, (b) Sharp dissection of the external oblique aponeurosis, (c) The exposed internal oblique muscle, (d) Internal oblique muscle dissection, (e) Exposed transverse abdominis muscle, (f) After the transverse abdominis muscle dissection, the transverse fascia is exposed

3.2.4 Abdominal Muscle Dissection Main procedure: This resembles the ATP approach in that the three layers of the abdominal muscle wall are dissected sequentially. The external oblique layer is mostly composed of aponeurosis rather than muscle. There is also a risk of peritoneal lacerations during the transverse abdominis muscle dissection because it is an anterior region of the abdomen compared to the ATP approach. Monopolar cautery or sharp ­dissection should be avoided when dissecting this layer (Fig. 21).

cations, like left iliac vein injuries* or hypogastric injuries†. The retroperitoneal approach consists of the following steps: 1) approaching the left iliac artery, 2) left iliac vein mobilization, and 3) disc space exposure.

(1) Approach the left iliac artery After the retroperitoneal space blunt dissection, the psoas muscle is palpated. The retroperitoneal fat covering the psoas muscle is medially retracted, and the psoas fascia is exposed. While preserving the psoas fascia plane, additional blunt dissection is per3.2.5 Retroperitoneal Approach formed at the anterior end of the psoas musMain procedure: The exposure of the peri-­ cle. The left iliac artery is palpable at the vertebra membrane during the L5/S1 approach medial end of the psoas muscle. The fat covcan be challenging during the initial learning ering the left iliac artery is dissected in the curve. This approach is related to serious complimedial direction. The iliac vein can be found

Oblique Lumbar Interbody Fusion (OLIF)

259

a

b

c

d

Fig. 22  Approach to the left iliac artery: (a) Exposed transverse fascia, (b) Blunt dissection of the retroperitoneal space, (c) Exposed psoas fascia, (d) Internal iliac

after lateral retraction of the iliac artery. The ureter is concurrently medially retracted together with the retroperitoneal fat (Fig. 22) (2) Left iliac vein mobilization [12] After obtaining a view of the deep corridor using a retractor with a light source, the potential fascia between the left iliac vein and peri-vertebral membrane is identified. When this fascia is spread by blunt dissection from the medial border of the iliac vein, it can be retracted laterally. Additional dissection of the iliac vein is necessary in case a wedge occurs on the medial edge during lateral retraction of the iliac vein (Fig. 23). (3) Disc space exposure Using a lightened medial blade and peanut, blunt dissection along the peri-vertebral membrane in the direction of the disc space is performed until sufficient annulotomy is possible. At this time, the median sacral vessel is identified, and this vessel is cut after bipolar cautery or vascular clips to sufficiently expose the entire surface of the L5/S1 disc space (Fig. 24). The right iliac vessel is located more laterally than the left, and thus medial retraction to the right iliac vessel is not required. Tip 1. Fixing the retractor is optional. The commercial retractor blades are attached to the three-way fixing arm on the opera-

e

artery exposed after psoas muscle retraction, (e) A schematic diagram of the retroperitoneal approach. Yellow: ureter, red: iliac artery, blue: iliac vein

tive table. The lateral and cephalad blade can be pinned to the vertebral body. Pinning the medial blade is not mandatory. Additionally, caution must be exercised due to the substantial risk of vessel injury during the pin insertion process. *It is important to understand the relationship between the psoas fascia and iliac vessel. The psoas fascia connects to the adventitia of the iliac vein, the iliac artery, and then to the connective tissue in front of the vertebral body. If the iliac vein is directly laterally retracted without opening this fascia, the medial margin of the iliac vein is wedged and resulting in an increased risk of iliac vein injuries. Additionally, in the absence of a fat pad under the left iliac vein, a risk of iliac vein injuries during dissection and lateral retraction remains. † The hypogastric nerve innervates the sympathetic nerve and runs into the retroperitoneal fat between the bilateral iliac veins. Hypogastric nerve injuries lead to increased bladder tone, impaired ejaculation, and dyspareunia. It is not clearly visible in the surgical field of view. To reduce hypogastric nerve injuries, clean dissections are needed to avoid the damage of fat layers between the iliac vein and peri-­

D. Son and S. Lee

260

a

b

c

d

Fig. 23  Left iliac vein mobilization; (a) The left iliac vein was exposed after internal iliac artery retraction, while the circle represents a potential plane extending above the iliac vein and peri-vertebra membrane, (b) A schematic diagram of the retroperitoneal approach:

a

b

Fig. 24  Disc space exposure: (a) The L5/S1 level is checked through the C-arm lateral image, (b) The L5/S1 mid-disc level is assessed through the C-arm AP image.

(arrow) anterior wedging of the iliac vein, (c) The potential fascia is opened, while the circular representation on the image was opened and peri-vertebra membrane was exposed, (d) A schematic diagram of the retroperitoneal approach: (arrow) Iliac vein mobilization

c

Blue arrow: middle sacral vessel, (c) A schematic diagram of the exposure of disc space. Red/blue point: middle sacral vessel

Oblique Lumbar Interbody Fusion (OLIF)

261

a

b

c

d

e

f

Fig. 25  Annulotomy and discectomy; (a) Incision on the annulus, (b) Annulotomy, (c) Schematic diagram of the annulotomy margin, (d, e) Checking the shaver position using the C-arm AP/lateral image, (f) Schematic diagram of extent of discectomy

vertebra membrane. Moreover, the use of bovie or sharp dissections should be avoided in this area.

3.2.6 Annulotomy and Discectomy Main procedure: After sufficiently exposing the disc space, the mid-disc point with C-arm AP images should be checked and marked on the L5 vertebra. The medial margin of the annulotomy is the center of the disc space, and the lateral margin is more than 20 mm lateral from the mid-­line*. A sufficiently large, square-shaped annulotomy is essential to prevent the “flapper valve phenomenon.” The disc and cartilage endplate should be removed using sequential shavers (Fig. 25).

Tip 2. If the left lateral area of the disc is not sufficiently secured due to the left lilac vein or narrow pelvis, the removal of total ALL may be necessary to insert the cage. In this case, there is a risk that the cage will be positioned close to the contralateral neural foramen during the oblique insertion of instruments. To prevent this, placing the instrument perpendicular to the disc space, like ALIF, helps to center the cage. *The mid-disc line was selected as the annulotomy medial margin because half of the remaining ALLs have ligamentotactic effects and serve as an anterior barrier to cage ventral migration during position change.

Tip 1. Since the annulotomy is typically performed only on the lateral half, discectomies should be performed in the oblique direction to obtain sufficient space for the cage entrance. However, unlike ALIF, the orientation can be confusing in this process. Since the instrument can enter the posterior spinal canal or contralateral neural foramen during the procedure, it should be performed while checking the position of instruments with the C-arm.

3.2.7 Sequential Trial Size Selection and Cage Insertion Main procedure: After obliquely combining the trial and inserter, the trial is inserted while paying close attention to the orientation. Sufficient disc height restoration or spondylolisthesis reduction is obtained by sequential trialing and distraction. The cage size and angle is determined by performing a manual pull-out test. After the endplate preparation using a rasp and curette, saline irriga-

D. Son and S. Lee

262

a

b

c

d

e

Fig. 26  Trialing and cage insertions; (a, b) Checking the trial position using the C-arm AP/lateral image, (c, d) Checking the final cage position using the C-arm AP/lateral image (e) Schematic diagram of the ideal cage position

tion of the operative corridor is performed. After filling the cage with DBM and inserting it in the oblique direction, the final position of the cage is confirmed with a C-arm image (Fig. 26). Tip 1. When the ALL is totally resected, the trial is attached anteriorly to the inserter and enters perpendicular to the disc space. Compared to the oblique insertion, the orientation is intuitive. However, since ALL is not left, anterior support, such as plating, or buttress screws are required.

3.2.8 Closure Process: While the process is the same as the ATP approach, tight sutures of aponeurosis are required.

4 Postoperative Consideration and Case Illustration 4.1 Case Illustration 1. Intercostal approach L2–3: A routine approach to L2/3 OLIF is occasionally possible, depending on the rib location, but the maintenance of parallel and orthogonal maneuvers is difficult. Additionally, accessing the L2/3 is challenging level due to the obstructions of the ribs in

numerous cases. In this case, L2/3 OLIF can be easily performed by approaching between ribs 11 and 12 (Fig. 27). (1) Preoperative planning: When planning the L2/3 OLIF approach, the descending extent of the left costophrenic recess should be evaluated using preoperative X-rays and CT images. Usually, in patients where the OLIF L2/3 approach is obstructed by the ribs, the rib cage is located considerably downward. In this case, the costophrenic recess rarely descends into the L2/3 surgical range. (2) Skin incision: Marking the L2/3 level through the C-arm. The ribs are marked by palpating around the L2/3 disc level. An incision line is designed between the ribs 11 and 12. (3) Dissection of chest wall: The subcutaneous skin, external intercostal muscle, internal intercostal muscle, and diaphragm lateral aponeurosis are approached in sequence. The layer-by-­ layer approach by spreading each muscle bundle. When the diaphragm aponeurosis is opened, retroperitoneal fat is confirmed. (Caution is necessary because the parietal pleura may descend between the internal intercostal muscle and diaphragm aponeurosis.)

Oblique Lumbar Interbody Fusion (OLIF)

263

a

b

e

c

d

f

Fig. 27  An intercostal approach for L2/3; (a) Retroperitoneal fat exposure after the chest wall muscle dissection, (b, c) Fixation of the retractors without pinning, (d) Cage insertion, (e, f) C-arm image obtained after cage insertion



(4) Retroperitoneal approach: After the retroperitoneal fat is retracted to the medial side, the psoas muscle is exposed. When the psoas muscle is retracted dorsally, the disc space is exposed. At this time, the commercially available OLIF25 retractor can be inserted between the ribs. When the retractor is distracted between the ribs, sufficient fixation force is obtained without pinning. (5) Cage insertion: After confirming the retractor location through the C-arm, annulotomy, discectomy, trialing, and cage insertions are performed, like conventional OLIFs. (6) Closure: The diaphragm aponeurosis is tightly sutured, and the internal/external intercostal muscles are also closed layer by layer. 2. Pre-psoas approach L5–S1: In L5/S1, if the IVC confluence or iliac vein is located anterior to the disc, BIB access is not possible. However, notably, ATP access is possible in selected cases. (Fig.  17b). Compared to the BIB approach, the ATP approach has a relatively shallow operative field and less risk of hypogastric nerve injuries. The ATP approach

has an increased risk of contralateral nerve root injuries, difficulty in attaining sufficient lordosis, and iliolumbar vein injuries (Fig. 28). (1) Preoperative planning: ATP access is possible when the disc space estimation exceeds 20  mm, after careful consideration of the fat below the iliac vein, the location of the vein, and the shape of the pelvis in preoperative images. Even if the vein location is suitable for ATP access, it is difficult to maintain an orthogonal maneuver when the ASIS is significantly prominent. In this case, the cage can be positioned in the contralateral neural foramen. (2) Skin incision: The L5/S1 disc level is marked using the C-arm. An incision line is designed in front of two fingers of the ASIS. (3) Dissection of the abdominal wall: Layer-­ by-­layer dissection is performed after the skin incision. The external oblique layer is composed of aponeurosis. Because the transverse muscle is close to the peritoneum, caution is required while using bovie or sharp dissections.

D. Son and S. Lee

264

a

b

c

d

e

f

g

h

i

Fig. 28  The anterior to psoas approach for L5/S1; (a) Exposure of the left iliac artery after retroperitoneal approach, (b) The iliac vein and iliolumbar vein (branch) confirmed after iliac artery retraction, (c, d) Clipping,

coagulation, and cutting of the iliolumbar vein, (e, f) Exposure of the disc space, (g) After the cage insertion, (h, i) C-arm images after cage insertion

(4) Retroperitoneal approach: ATP and BIB are different in terms of the retroperitoneal approach. The BIB dissections are typically medial to the left iliac vessel. In contrast, the ATP approach dissects between the lateral side of the iliac vessel and psoas muscle. (5) Annulotomy: To secure an adequate annulotomy margin, the psoas muscle is retracted laterally. When the iliac vein requires medial retractions for adequate annulotomy margins, the iliolumbar vein must be found and ligated. An increased risk of massive bleeding remains if the medial retraction is performed without the ligation of the Iliolumbar vein. (6) Cage insertion: If the annulotomy margin and orthogonal maneuver are estimated as sufficient for cage insertion, subse-

quent annulotomy, shaving, and trialing are performed in order. The width and length of the cage is selected such that the contralateral neural foramen is not closed. (7) Closure: The external oblique aponeurosis requires tight sutures, and the other abdominal muscles are also closed layer by layer.

5 Summary OLIF approach has some difficulties in retroperitoneal approach when initially experience for the spine surgeon. Additionally, reports on the ASD-­ related long-term results of OLIF are insufficient. However, the learning curve for OLIF is relatively easy compared to the posterior approach. OLIF can have a multilevel approach through a

Oblique Lumbar Interbody Fusion (OLIF)

single corridor, which is advantageous in terms of the EBL and operative times when compared to posterior interbody fusions, which requires a separate channel. Understanding the procedures and complications of OLIF will provide an effective and safe arm for spine surgeons.

References 1. Gragnaniello C, Seex K.  Anterior to psoas (ATP) fusion of the lumbar spine. In: Lateral access minimally invasive spine surgery. Springer; 2017. p. 111–125. 2. Hynes RA.  Oblique lateral approach to the lumbar spine (L2–L5). In: Surgical approaches to the spine. Springer; 2015. p. 223–234. 3. Quillo-Olvera J, Lin G-X, Jo H-J, Kim J-S.  Complications on minimally invasive oblique lumbar interbody fusion at L2–L5 levels: a review of the literature and surgical strategies. Ann Transl Med. 2018;6(6):101. 4. Molinares DM, Davis TT, Fung DA, Liu JC-L, Clark S, Daily D, et  al. Is the lateral jack-knife position responsible for cases of transient neurapraxia? J Neurosurg Spine. 2016;24(1):189–96. 5. Feigl G, Kastner M, Ulz H, Breschan C, Dreu M, Likar R. Topography of the lumbar sympathetic trunk

265 in normal lumbar spines and spines with spondylophytes. Br J Anaesth. 2011;106(2):260–5. 6. Gandhi K, Verma V, Chavan S, Joshi S, Joshi S.  The morphology of lumbar sympathetic trunk in humans: a cadaveric study. Folia Morphol (Warsz). 2013;72(3):217–22. 7. Wang H, Zhang Y, Ma X, Xia X, Lu F, Jiang J.  Radiographic study of lumbar sympathetic trunk in oblique lateral interbody fusion surgery. World Neurosurg. 2018;116:e380–e5. 8. Hynes RA. Oblique lateral retroperitoneal approach to L5–S1. In: Surgical approaches to the spine. Springer; 2015. p. 235–241. 9. Mun HY, Ko MJ, Kim YB, Park SW.  Usefulness of oblique lateral interbody fusion at L5–S1 level compared to transforaminal lumbar interbody fusion. J Korean Neurosurg Soc. 2020;63(6):723. 10. Orita S, Shiga Y, Inage K, Eguchi Y, Maki S, Furuya T, et al. Technical and conceptual review on the L5-S1 oblique lateral interbody fusion surgery (OLIF51). Spine Surg Relat Res. 2021;5(1):1–9. 11. Chung N-S, Jeon C-H, Lee H-D, Kweon H-J.  Preoperative evaluation of left common iliac vein in oblique lateral interbody fusion at L5–S1. Eur Spine J. 2017;26(11):2797–803. 12. Ko MJ, Park SW, Wui SH.  An anatomical clue for minimizing iliac vein injury during the anterolateral approach at L5–S1 level: a cadaveric study. Neurospine. 2021;18(4):833.

Minimally Invasive Adult Spinal Deformity Correction Junseok Bae

1 Introduction Adult spinal deformity (ASD) is a complex of various degenerative pathology with spinal stenosis, multilevel disc degeneration, facet arthropathy, osteoporosis, coronal scoliosis, and sagittal plane deformity. The presence of spinal deformity negatively impacts on patient’s daily life causing significant disability, especially in the elderly. Conservative treatment often fails in improving quality of life in advanced deformity. However, accompanying comorbidity in the elderly are related to serious postsurgical complication as high as 80% for complex surgical procedures. Minimally Invasive Surgery (MIS) for ASD has made significant progress over the past decade with the development of various technologies. MIS approach for ASD patients does not result in inferior outcomes compared to open surgeries. Various surgical approaches and techniques are applied in different degenerative disease categories. Therefore, different surgical skill sets have resulted in achieving more optimal surgical results. MIS interbody fusion became increasingly utilized in ASD to achieve greater restoration of disc height, segmental lordosis, and neural decompression. Additional spinal instrumentation reinforces corrective power and

J. Bae (*) Department of Neurosurgery, Cheongdam Wooridul Spine Hospital, Seoul, Republic of Korea

construct stability. To optimize treatment goals, different algorithms have been developed to guide surgeons on appropriate patient selection. Recent advances in surgical instrument and decision-­making process achieved optimal clinical and radiological outcomes in selected patients without open surgery. Understanding of good indications for MIS approach and selection of proper surgical method is important.

2 Indications The goals of ASD treatment are to achieve adequate neural decompression, restoring or maintaining sagittal and coronal balance, and achieving bone union. Mummaneni et  al. suggested an algorithm for minimally invasive spinal deformity surgery [1, 2]. Based on preoperative radiological parameters, patients were stratified into different surgical strategies, ranging from MISS decompression only or selective fusion to open surgery with osteotomies. MISS technique is frequently utilized for patients with smaller coronal deformities, a sagittal vertical axis under 6 cm, a baseline pelvic incidence—lumbar lordosis mismatch under 30°, and a pelvic tilt of under 25°. For patients with symptoms of central and lateral recess stenosis or foraminal stenosis accompanying mild spinal deformity, neural decompression is a treatment goal. MIS decom-

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_24

267

268

pression technique can be utilized for these patients. Decompression using tubular retraction system or 1-level MIS fusion may be a treatment option. 1 Circumferential MIS (cMIS) technique is composed of 360° deformity correction with anterior interbody support and posterior instrumentation through MIS approach. Lateral lumbar interbody fusion (LLIF) followed by percutaneous pedicle screw fixation with additional lumbosacral interbody fusion by transforaminal interbody fusion gets the most popularity in cMIS.  The hybrid approach includes multilevel LLIF and posterior open instrumentation with or without osteotomies. In ASD with moderate sagittal deformity, satisfactory radiographic outcomes can be achieved similarly and adequately with a posterior spinal fixation (PSF)-only approach, a posterior approach combined with LLIF, or a posterior approach combined with anterior lumbar interbody fusion. Compared with patients treated with an ALIF+PSF or PSF-only surgical strategy, patients who underwent LLIF+PSF had lower rates of proximal junctional kyphosis and mechanical failure at the upper instrumented vertebra and less back pain, less disability, and better SRS-22 scores. The selection of which interbody approach is appropriate is dependent on several factors: patient’s body habitus, previous surgical history, bony and vascular anatomy, surgeon experience, and addressed pathology. A recent research showed surgeons preferred LLIF for L1–4 levels. For L5-S1, ALIF was preferred when segmental lordosis was desired. For L4–5, LLIF, TLIF, and ALIF were preferred in order but various surgical variables should be considered [1, 3–6].

3 Lateral Lumbar Interbody Fusion For ASD, LLIF is a powerful correction method in both coronal and sagittal plane deformity [3, 6–13]. The lateral trans-psoas approach is direct lateral approach via splitting psoas muscle, whereas the oblique anterior-psoas approach is oblique lateral approach anterior to the psoas muscle. Both approaches are retroperitoneal

J. Bae

approaches to the disc space via lateral annulus allowing for discectomy, distraction, and interbody fusion. LLIF can restore intervertebral disc height resulting in indirect decompression of neural foramina without jeopardizing segmental stability because it retains the ALL and PLL.  Furthermore, wide interbody cages that support the lateral rims of the endplate can be placed via the lateral approach, which may translate into prevention of subsidence and subsequent loss of deformity correction. In this respect, degenerative scoliosis is a main indication of LLIF.  Many authors reported successful radiological and clinical outcomes following LLIF and posterior instrumentation for indirect decompression and realignment of coronal balance. However, the effects on sagittal balance and spinopelvic parameters are often reported to be limited. Anand et al. presented long-term follow-up results of MIS technique for adult scoliosis [14]. They did LLIF followed by the posterior instrumentation and fusion with axial lumbar interbody fusion for coronal deformity without sagittal malalignment. The mean preoperative Cobb angle was 24.7°, which corrected to 9.5°. The mean preoperative Coronal balance was 25.5 mm, which corrected to 11 mm. The mean preoperative sagittal balance was 31.7 mm and corrected to 10.7  mm. At 2- to 5-year follow-up, they reported comparable correction of adult spinal deformity significantly improved functional outcomes, and excellent clinical and radiological improvement, but considerably lowers morbidity and complication rates. Although some authors reported improvement in sagittal spinopelvic parameters, most of the patients exhibited main coronal plane deformity without sagittal imbalance or with mild sagittal imbalance due to severe sagittal imbalance is not adequately treated with MIS approach (Fig. 1). LLIF with anterior column realignment (ACR) is a technique for correction of sagittal plane deformity, which is performed via lateral trans-­ psoas approach with anterior longitudinal ligament release and hyperlordotic (20–30°) cage placement [15–20]. LLIF with ACR can restore higher degrees of segmental lordosis and can be applied as a minimally invasive alternative to

Minimally Invasive Adult Spinal Deformity Correction

269

a

b

Fig. 1  Case presentation of circumferential minimally invasive surgery for degenerative lumbar scoliosis. (a) Preoperative A-P and lateral EOS scan showing severe rotational deformity at L3 and L4 level with compensatory rotation TL junction. (b) After lateral lumbar inter-

body fusion at the L2–3, L3–4, and L4–5 level, vertebral rotation (right upper) at the L3 and L4 was restored as well as coronal alignment (right lower). (c) Percutaneous pedicle screw fixation was addressed at the index level, resulting in stability and improvement of coronal balance

J. Bae

270

c

Fig. 24.1 (continued)

posterior osteotomy techniques in selected patients. Average 16.3° and 5.7° segmental lordosis were increased by LLIF with and without ACR, respectively. Patients with ACR and MIS percutaneous pedicle screw stabilization had a segmental lordosis increase of 9.9°. With ACR, LL can increase by 81% of the segmental lordosis gain when using hyperlordotic cages, with an improvement in the PI-LL mismatch by 8.3°. Recent research showed the greatest segmental lordosis was achieved via ACR at L2–3 and L3–4, suggesting those two levels are the most likely candidates for the ACR [16]. Hybrid surgery performing posterior column osteotomy with ACR achieved more segmental lordosis than cMIS correction with ACR and percutaneous pedicle fixation but the subsidence rate was increased as a counterforce. ACR-related complications are rarely reported in experienced hands, but the vascular injury can cause catastrophic outcomes thus vascular intervention should be immediately performed in case. Single-position circumferential lumbar interbody fusion is recruiting recent interest in benefit of shorter operating time and hospital stay while

maintaining similar perioperative outcomes. Prone single-position lateral lumbar interbody fusion is designed for simultaneous access to the anterior and posterior lumbar spine allowing lateral lumbar interbody cage placement, direct posterior decompression, and instrumentation [21, 22]. However, there is a clear limitation for applying this technique in major deformity except for spondylolisthesis or segmental scoliosis correction.

4 Lumbosacral Interbody Fusion Option Mummaneni et al. reported MIS TLIF is the most common procedure at L5-S1 level, followed by ALIF [1]. Their result showed the increase in segmental lordosis at L5–S1 was significantly greater with ALIF than with TLIF (5.3° vs. 1.9°). It is well known that MIS TLIF is often used as an adjunct to multilevel LLIF or MIS posterior approaches for ASD. For MIS TLIF, a systematic review showed mean increases in segmental lordosis for static and expandable cages of 2.1° and 5.0°, respectively. Wang et al. reported significant

Minimally Invasive Adult Spinal Deformity Correction

improvement in sagittal balance with multilevel facet osteotomies and MIS TLIF in addition to percutaneous screw fixation for ASD [23]. ALIF offers several advantages over LLIF, including direct decompression of neural foramina, accessibility to L5-S1, less mobilization of the psoas muscle, resection of the ALL, wide discectomies, and insertion of wedge-shaped lordotic grafts that result in greater segmental lordosis restoration in the lower lumbar spine compared with TLIF.  However, it does carry risks related to mobilization of the abdominal viscera and large vessels. Anand et al. reported a presacral approach for discectomy and interbody fusion with low risk of surgical morbidity. However, supporting literature on this technique for ASD is not sufficient. LLIF is rarely utilized at the L5-S1 given approach constraints from the iliac crest and complex vascular anatomy.

5 Percutaneous Pedicle Screw Placement Although some selected patients are benefitable for stand-alone LLIF without posterior instrumentation, most of ASD patients need to be stabia

b

Fig. 2  Preoperative anterior-posterior (a) and lateral (b) radiographs show rigid deformity on both coronal and sagittal plane. Lateral lumbar interbody fusion from L1 to L4 and anterior lumbar interbody fusion from L4 to S1 was performed to restore anterior disc height. Additionally,

271

lized and further corrected posteriorly with pedicle screw instrumentations. Percutaneous pedicle screw instrumentation is important for circumferential MIS (cMIS) deformity surgery. Various correction maneuvers including vertical translation of apex, rebalancing of both coronal and sagittal plane with compression, distraction, and direct derotation are applicable following LLIF.  For rigid lumbosacral fixation in cMIS, Wang et al. reported feasibility and safety of percutaneous iliac screw placement without extensive muscle exposure [24]. Hybrid surgery is a good surgical alternative to open posterior or cMIS correction [25–29]. It utilizes MIS interbody approaches with traditional open posterior instrumentation and osteotomies necessary. Uribe et  al. compared ASD undergoing cMIS versus open surgeries [25]. Their result showed construct lengths could be halved with cMIS, due in part to the increased use of interbody grafts. The cMIS group achieved similar clinical outcomes, similar complication rates, and significantly improved PI-LL correction compared with the open surgery group (Fig. 2). Fluoroscopic guidance is essential in percutaneous pedicle screw placement. Recent advances in image-guided surgery with navigation or c

d

open posterior segmental instrumentation from T10 to iliac fixation with multilevel grade 2 osteotomies was done to release posterior column mobility and further correction. Postoperative anterior-posterior (c) and lateral (d) radiographs show well-balanced coronal and sagittal curvature

J. Bae

272

robotic guidance enhance safety and accuracy of the surgery. MIS deformity correction essentially limits exposure and visualization, navigation and robotics play a clear role in improving implant accuracy, reduced operative time, and lower intraoperative radiation exposure [30–32]. Some study showed no statistical advantage for reduced radiation exposure to the patient by robotics and navigation, the radiation exposure to the surgical team is greatly reduced. Because navigation and robotic assistive procedures allow surgeons and teams to maintain a safe distance from radiation sources, these procedures are associated with negligible levels of radiation and may limit repeated exposure while maintaining implant accuracy.

6 Outcomes and Complications Ever since Dakwar et al. reported the feasibility of LLIF for adult degenerative scoliosis, for properly indicated patients, MIS approach achieved good clinical and radiological outcomes. Anand et  al. reported mean 48  months follow-up results after cMIS for moderate (Cobb angle between 30° and 75°) adult scoliosis [33]. Mean Cobb angle and sagittal vertical axis were decreased from 42° and 51 mm preoperatively to 16° and 27  mm postoperatively. HRQoL scores were also improved at the last follow-up with considerably lower morbidity and complication rates. However, cMIS procedure had the limitation of correction in both coronal and sagittal plane deformity. Careful decision-making for choosing surgical approach is mandatory in tailoring goals of deformity correction according to patients’ radiological and clinical status. For similar baseline deformity, cMIS exhibits reduced construct length, reoperation rate, costs, blood loss, and hospital stays with comparable clinical radiological improvement. Uribe et al. reported a significant decrease in mean fusion levels (4.8 for cMIS vs. 10.1 open), blood loss (488 mL cMIS vs. 1762  mL open), and hospital stay (6.7  days cMIS vs. 9.7  days open) in cMIS.  Due to decreased surgery-related morbidity, older

patients can benefit from MIS approach for ASD in terms of HRQoL improvement. Major complications such as massive bleeding and postsurgical infection rate is relatively less in cMIS than in open surgery. However, a complication related to surgical approach especially for LLIF should be considered. Iliopsoas weakness, temporary paresthesia, dysesthesia, or numbness on thigh has been reported ranging from 12.5% to 75% with LLIF.  Pseudarthrosis is a major issue for long-­ term outcomes after ASD surgery. Fusion rate after cMIS surgery widely ranges from 71.4% to 100%, while overall fusion rate after ASD surgery is reported to be 93.7% (ranges from 59% to 100%). The use of bone graft substitute such as rhBMP-2 helps to enhance the fusion rate [34]. Mummaneni et al. showed that pseudarthrosis is higher in cMIS compared with hybrid group (46.% vs. 71.6%) and the overall incidence of PJK (48.1% vs. 53.8%) and reoperation for PJK (11.1% vs. 19.2%) is similar in cMIS and hybrid group [35]. Bae et al. showed hybrid surgery utilizing LLIF had lower rates of PJK and mechanical failure at the upper instrumented vertebra and better HRQoL scores in comparison with open posterior surgery and hybrid surgery using ALIF, while radiological improvement was similar between three different surgeries for ASD with moderate sagittal imbalance [36]. In comparison with open posterior surgery, hybrid surgery with LLIF showed faster recovery, fewer complications, and greater relief of pain and disability.

7 Summary Recent advances in various technologies have helped induce minimally invasive approaches in ASD.  These techniques have been transformed into comparable clinical and radiologic outcomes compared to laparotomy in some of the less demanding deformities. Selecting a proper approach for the specific type of deformity has produced repeatable and safe results. Given currently published literature, efficacy and limitations of MIS approach is clear. Surgeons should understand the roles of various types of surgery to gain the goals of defor-

Minimally Invasive Adult Spinal Deformity Correction

273

open posterior surgery for adult spinal deformity. J Neurosurg Spine. 2016;25(6):697–705. 10. Uribe JS, Deukmedjian AR.  Visceral, vascular, and wound complications following over 13,000 lateral interbody fusions: a survey study and literature review. Eur Spine J. 2015;24(Suppl. 3):386–96. 11. Caputo AM, Michael KW, Chapman TM, et  al. Extreme lateral interbody fusion for the treatment of adult degenerative scoliosis. J Clin Neurosci. 2013;20(11):1558–63. 12. Amin BY, Mummaneni PV, Ibrahim T, Zouzias A, Uribe J.  Four-level minimally invasive lateral interbody fusion for treatment of degenerative scoliosis. Neurosurg Focus. 2013;35(Suppl. 2) Video 10 References 13. Isaacs RE, Hyde J, Goodrich JA, Rodgers WB, Phillips FM.  A prospective, nonrandomized, multicenter evaluation of extreme lateral interbody fusion 1. Mummaneni PV, Hussain I, Shaffrey CI, et  al. The for the treatment of adult degenerative scoliosis: minimally invasive interbody selection algorithm for perioperative outcomes and complications. Spine. spinal deformity. J Neurosurg Spine. 2021:1–8. 2010;35(26 Suppl):S322–30. 2. Mummaneni PV, Shaffrey CI, Lenke LG, et  al. The minimally invasive spinal deformity surgery algo- 14. Anand N, Baron EM, Khandehroo B, Kahwaty S. Long-term 2- to 5-year clinical and functional outrithm: a reproducible rational framework for decision comes of minimally invasive surgery for adult scoliomaking in minimally invasive spinal deformity sursis. Spine. 2013;38(18):1566–75. gery. Neurosurg Focus. 2014;36(5):E6. 3. Park SW, Ko MJ, Kim YB, Le Huec JC. Correction of 15. Turner JD, Akbarnia BA, Eastlack RK, et  al. Radiographic outcomes of anterior column realignmarked sagittal deformity with circumferential miniment for adult sagittal plane deformity: a multicenter mally invasive surgery using oblique lateral interbody analysis. Eur Spine J. 2015;24(Suppl 3):427–32. fusion in adult spinal deformity. J Orthop Surg Res. 16. Saigal R, Mundis GM Jr, Eastlack R, Uribe JS, 2020;15(1):13. Phillips FM, Akbarnia BA. Anterior column realign4. Ohba T, Ebata S, Ikegami S, Oba H, Haro H. ment (ACR) in adult sagittal deformity correcIndications and limitations of minimally invation: technique and review of the literature. Spine. sive lateral lumbar interbody fusion without oste2016;41(Suppl 8):S66–73. otomy for adult spinal deformity. Eur Spine J. 17. Mundis GM Jr, Turner JD, Kabirian N, et al. Anterior 2020;29(6):1362–70. column realignment has similar results to pedicle 5. Lee KY, Lee JH, Kang KC, et al. Minimally invasive subtraction osteotomy in treating adults with sagittal multilevel lateral lumbar interbody fusion with posplane deformity. World Neurosurg. 2017;105:249–56. terior column osteotomy compared with pedicle subtraction osteotomy for adult spinal deformity. Spine J. 18. Godzik J, Pereira BA, Newcomb A, et al. Optimizing biomechanics of anterior column realignment for 2020;20(6):925–33. minimally invasive deformity correction. Spine J. 6. Anand N, Alayan A, Agrawal A, Kahwaty S, Nomoto 2020;20(3):465–74. E, Khandehroo B.  Analysis of Spino-pelvic parameters and segmental lordosis with L5-S1 oblique lat- 19. Godzik J, de Andrada PB, Sawa AGU, Lehrman JN, Mundis GM, Hlubek RJ, et al. Biomechanics of open eral interbody fusion at the bottom of a long construct versus minimally invasive deformity correction: comin circumferential minimally invasive surgical corparison of stability and rod strain between pedicle rection of adult spinal deformity. World Neurosurg. subtraction osteotomy and anterior column realign2019;130:e1077–e83. ment. J Neurosurg Spine. 2021:1–9. 7. Theologis AA, Mundis GM Jr, Nguyen S, et  al. Utility of multilevel lateral interbody fusion of the 20. Berjano P, Cecchinato R, Sinigaglia A, et al. Anterior column realignment from a lateral approach for the thoracolumbar coronal curve apex in adult defortreatment of severe sagittal imbalance: a retrospecmity surgery in combination with open posterior tive radiographic study. Eur Spine J. 2015;24(Suppl instrumentation and L5-S1 interbody fusion: a case-­ 3):433–8. matched evaluation of 32 patients. J Neurosurg Spine. 21. Ziino C, Konopka JA, Ajiboye RM, Ledesma JB, 2017;26(2):208–19. Koltsov JCB, Cheng I.  Single position versus 8. Than KD, Nguyen S, Park P, et  al. 165 what is the lateral-­ then-prone positioning for lateral interbody effect of open vs percutaneous screws on complicafusion and pedicle screw fixation. J Spine Surg. tions among patients undergoing lateral interbody 2018;4(4):717–24. fusion for adult spinal deformity? Neurosurgery. 22. Lamartina C, Berjano P.  Prone single-position 2016;63(Suppl 1):166. extreme lateral interbody fusion (pro-XLIF): prelimi9. Strom RG, Bae J, Mizutani J, Valone F 3rd, Ames CP, nary results. Eur Spine J. 2020;29(Suppl 1):6–13. Deviren V.  Lateral interbody fusion combined with

mity correction as well as reducing complications. The progressive development of devices, navigation, and appropriate patient selection will continue to advance this field. The deployment of multicenter networks further strengthened research in large numbers of patients to establish the advantages and limitations of MIS.

274 23. Wang MY, Uribe J, Mummaneni PV, et al. Minimally invasive spinal deformity surgery: analysis of patients who fail to reach minimal clinically important difference. World Neurosurg. 2020;137:e499–505. 24. Wang MY, Williams S, Mummaneni PV, Sherman JD.  Minimally invasive percutaneous iliac screws: initial 24 case experiences with CT confirmation. Clin Spine Surg. 2016;29(5):E222–5. 25. Uribe JS, Deukmedjian AR, Mummaneni PV, et al. Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques. Neurosurg Focus. 2014;36(5):E15. 26. Haque RM, Mundis GM Jr, Ahmed Y, et  al. Comparison of radiographic results after minimally invasive, hybrid, and open surgery for adult spinal deformity: a multicenter study of 184 patients. Neurosurg Focus. 2014;36(5):E13. 27. Hamilton DK, Kanter AS, Bolinger BD, et  al. Reoperation rates in minimally invasive, hybrid and open surgical treatment for adult spinal deformity with minimum 2-year follow-up. Eur Spine J. 2016;25(8):2605–11. 28. Chan AK, Eastlack RK, Fessler RG, et al. Two- and three-year outcomes of minimally invasive and hybrid correction of adult spinal deformity. J Neurosurg Spine. 2022;36(4):595–608. 29. Barone G, Scaramuzzo L, Zagra A, Giudici F, Perna A, Proietti L.  Adult spinal deformity: effectiveness of interbody lordotic cages to restore disc angle and spino-pelvic parameters through completely mini-­ invasive trans-psoas and hybrid approach. Eur Spine J. 2017;26(Suppl 4):457–63.

J. Bae 30. Pham MH, Shah VJ, Diaz-Aguilar LD, Osorio JA, Lehman RA.  Minimally invasive multiple-­ rod constructs with robotics planning in adult spinal deformity surgery: a case series. Eur Spine J. 2022;31(1):95–103. 31. Hyun SJ, Kim KJ, Jahng TA.  S2 alar iliac screw placement under robotic guidance for adult spinal deformity patients: technical note. Eur Spine J. 2017;26(8):2198–203. 32. Oh T, Park P, Miller CA, Chan AK, Mummaneni PV.  Navigation-assisted minimally invasive ­surgery deformity correction. Neurosurg Clin N Am. 2018;29(3):439–51. 33. Anand N, Rosemann R, Khalsa B, Baron EM. Mid-­ term to long-term clinical and functional outcomes of minimally invasive correction and fusion for adults with scoliosis. Neurosurg Focus. 2010;28(3):E6. 34. Mulconrey DS, Bridwell KH, Flynn J, Cronen GA, Rose PS.  Bone morphogenetic protein (RhBMP-2) as a substitute for iliac crest bone graft in multilevel adult spinal deformity surgery: minimum two-year evaluation of fusion. Spine. 2008;33(20):2153–9. 35. Mummaneni PV, Park P, Fu KM, et  al. Does minimally invasive percutaneous posterior instrumentation reduce risk of proximal junctional kyphosis in adult spinal deformity surgery? Neurosurgery. 2016;78(1):101–8. 36. Bae J, Theologis AA, Strom R, et  al. Comparative analysis of 3 surgical strategies for adult spinal deformity with mild to moderate sagittal imbalance. J Neurosurg Spine. 2018;28(1):40–9.

Spinal Blocks and Radiofrequency Techniques Seungchan Yoo and Jong Tae Kim

1 Epidural Steroid Injection 1.1 Introduction Epidural injection, since its first report by Evans in 1930 [1], has served over several decades as an important therapeutic technique for radicular pain caused by spinal diseases. Radicular pain is caused by the nerve root compression itself as mediated by the herniated disc, while the inflammation or ischemia around the compressed nerve root is also known to play a critical role in the generation of radicular pain [2, 3]. This provides the basis for applying corticosteroid to the area of the affected root in the treatment of radicular pain [4]. The same mechanism underlies the effect of epidural injection in alleviating lower back pain caused by annular tear [5]. There are two approaches to epidural injection; the transforaminal approach and the interlaminar approach. While the former is slightly more technically demanding than the latter, it is superior regarding short-term pain relief as it allows more direct injections to the irritated nerve root [6, 7]. The details of the technique will be discussed subsequently. Selective nerve root block is technically almost identical to transforaminal epiS. Yoo · J. T. Kim (*) Incheon St. Mary’s Hospital, The Catholic University of Korea, Incheon, Republic of Korea e-mail: [email protected]

dural injection, and the two techniques will be discussed concomitantly.

1.2 Anatomy Epidural space is defined as the space between the dura mater and the vertebral bone, from the foramen magnum to the sacrococcygeal ligament. The space is filled with thecal sac, epidural fat, venous plexus, areolar tissue, and ligament flavum (Fig. 1). In the interlaminar approach, the epidural space is approached mainly through the midline, whose ligament flavum is the thinnest whereas the epidural fat is the thickest. The approach from the lateral side predicts reduced epidural fat and deeper and thicker ligament flavum, i.e., deeper and narrower epidural space. Compared to the lumbar spine, the cervical spine has narrower epidural space and among cervical spines, the higher level shows narrower epidural space. In the cervical epidural space, the thickness of the AP dimension is 2–3 mm, while it is 5–6 mm in the lumbar epidural space [8]. For this reason, interlaminar epidural injection is not performed on levels above C2 and C3. The roof and floor of the foramen comprise the upper and lower vertebral pedicles. The ventral border consists of the upper vertebra and the disc; the posterior border consists of the articular process (superior articular process in the cervical

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_25

275

S. Yoo and J. T. Kim

276 Fig. 1  Anatomy of spinal canal and epidural space

Spine dura Spine cord

Ligamentum flavum

Venous plexus Epidural fat

Interspinous ligament

Posterior longitudinal ligament

Supraspinous ligament

Exiting nerve root

Intervertebral disk

spine; inferior articular process of upper vertebra and superior articular process of lower vertebra in the lumbar spine). The cervical nerve root passes through the lower part of the foramen, while the epiradicular vein is found above the top of the foramen. As the vertebral artery is just lateral to the foramen and just anterior to the articular pillar, care should be taken not to cause an injury in the cervical foraminal approach. Adamkiewicz artery is the largest anterior segmental medullary artery that supplies blood to the lower two-thirds of the spinal cord. Its main course is the T9–L1 foramen on the left side, but care should be taken as there are reports on its course into the spinal canal on the T7–L4 level [9].

1.3 Medication The epidural injection uses a mixture of corticosteroid, local anesthetics, preservative-free saline, and others, among which corticosteroid plays the most central role. Corticosteroid reduces inflammation via the inhibition of the phospholipase A2 activity, which is its key mechanism of action, but it is also known to have a local anesthetic effect [10]. The most frequently used steroid in epidural injection is

methylprednisolone or triamcinolone. The most common therapeutic dose range is 40–80  mg, which is reported to be safe as well as effective [11]. However, care should be taken as there is a report on brain and spinal infarction cases as a result of intra-articular injection of particulate steroid as an unintended effect [12]. Dexamethasone is mainly selected as the nonparticulate steroid in epidural injection at a 4 mg dose [11]. Corticosteroids are generally used in a mixture of local anesthetics or saline. The total injection volume is 3–5 mL in the cervical or lumbar epidural block and 5 mL or above in caudal block [8]. Care should be taken however as it is known that local anesthetics in high cervical lesions could cause total spinal anesthesia, cardiorespiratory compromise, or loss of consciousness [11].

1.4 Indication and Contraindication The most common indication is a herniated disc or foraminal stenosis that could give rise to inflammation around nerve roots. The epidural steroid injection may be applied in the treatment of patients with neurogenic claudication due to central spinal stenosis. It may also be used for

Spinal Blocks and Radiofrequency Techniques

diagnostic purposes in the case of multilevel pathology or vague symptoms as a means to accurately locate the lesion, although SNRB is generally the preferred choice. The indications do not vary between the interlaminar and transforaminal approaches. Nevertheless, as the drug could disperse sideways from the midline—especially, at the injection of 5  mL or above—in the interlaminar approach, this is the approach more widely recommended for neurogenic claudication or bilateral radicular pain via central pathology [8]. The absolute contraindications are the injection to the area of systemic or localized infection as abscess formation may result and patients with a bleeding disorder or anticoagulation treatment as epidural hematoma may result. The presence of local malignancy in the injection area or allergy to the drug or contrast are other contraindications.

1.5 Interlaminar Approach 1.5.1 Technique: Cervical Interlaminar Epidural Injection The patient is guided to face the floor in a prone position and the C-arm is adjusted in the 15–20° a

277

caudal direction via rotation to allow optimum visualization of the interlaminar space. After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. The midpoint of the adjacent spinous processes is targeted for the insertion of an 18- or 20-gauge Tuohy needle. The needle is advanced until it reaches the interspinous ligament, while its position on the midline is checked on the C-arm AP image (Fig. 2). With the spinal needle safely touching the ligament, a syringe filled with a small amount of saline is connected to the needle, then the needle is advanced 1–2 mm at a time. After the advancement of 5–10 mm or more, the position of the needle is photographed again by rotating the C-arm to a full lateral view. On reaching the epidural space, the saline is seen to be sucked in “loss of resistance technique.” Once the needle tip appears to have reached the epidural space, 1–1.5 mL of nonionic radiographic contrast is injected, then the epidural spread is confirmed on the C-arm image. The steroid is slowly injected into a mixture with local anesthetics and saline. Care should be taken in using local anesthetics as there is a possibility of complications such as total spinal anesthesia. b

Fig. 2 (a) AP image of cervical interlaminar epidural injection. Black dash circle: spinous process/white dash line: interlaminar space. (b) Epidural spread of contrast in lateral image

S. Yoo and J. T. Kim

278

1.5.2 Technique: Lumbar Interlaminar Epidural Injection The patient is guided towards a prone position with the head turned to one side or adjusted straight. A pillow is placed below the mid and lower abdomen so as to widen the spinous process and reduce lordosis. The C-arm on the axial plane is 15–20° caudally rotated to allow optimum visualization of the interlaminar space. After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. As in the cervical interlaminar approach, the midpoint of the adjacent spinous process is targeted for the insertion of an 18- or 20-gauge Tuohy needle. The spinal needle is advanced until it reaches the interspinous ligament, while the needle tip is checked not to escape the midline on the C-arm AP image. Next, while checking the lateral image by rotating the C-arm, the needle is advanced towards the junction between the spinous process and the lamina. Here, the loss of resistance technique is applied. The spinal needle is connected to the syringe filled with 1–3 mL of saline and as the needle tip enters the epidural space, the saline is seen to be sucked in. Of note is that, at 25.7% unguided “loss of resistance” injection, the needle may not be placed in the epidural space [13] so that it should be confirmed on the image after the injection of contrast. Once the epidural spread is confirmed on the AP and lateral images after the injection of nonionic contrast, a 5 mL mixture of corticosteroid with local anesthetics and saline is prepared and injected. 1.5.3 Technique: Caudal Block The caudal approach is mainly used in the case where the target is the sacral nerve or a direct approach to the lumbar epidural space is ­challenging due to the history of osteoarthritis or spinal surgery. As in the lumbar epidural block, the patient is guided towards a prone position with the head turned to one side or adjusted straight. The C-arm is rotated in the 20–30° caudal direction to allow the visualization of the sacrum, sacral hiatus, and coccyx. The palpation of sacral cornua located slightly above the gluteal cleft could be helpful in locating the sacral hia-

tus. If it is difficult to distinguish the sacral hiatus on the AP image, the lateral image should be used to identify the sacral hiatus. After skin preparation and draping in a sterile manner, the skin that covers the sacral hiatus is anesthetized using 1% lidocaine. An 18-, 20-gauge Tuohy needle or a 22-gauge spinal needle is advanced towards the sacral hiatus. When the needle passes through the caudal sacrococcygeal ligament, a characteristic “pop” can be sensed to signal the entrance of the needle to the epidural space. The needle angle should be reduced to a level similar to the plane of the sacrum and the needle is advanced 1–2 cm further within the caudal epidural space (Fig.  3). Here, the accurate needle position can be confirmed through the injection of nonionic contrast. For advancing the lower lumbar legion, a thicker needle (17-gauge) is positioned in the caudal canal using the same method, and the flexible catheter with a stylet is advanced to the target location through the needle. The contrast is injected to confirm the accurate position of the tip of the catheter, after which the medication is injected (Fig. 4).

Sacrococcygeal ligament

Fig. 3  At first, it advances at an angle of about 40° to the axial plane, and when the sacrococcygeal ligament is penetrated, it is laid down at the same angle as the sacral plane (about 75°) and advanced

Spinal Blocks and Radiofrequency Techniques

279

Fig. 4  AP and lateral images of epidural spread after needle positioning for caudal injection

1.5.4 Complication The potential complications of interlaminar epidural injection include direct trauma to the spinal cord, dural puncture, epidural hematoma, and infection. If spinal cord injury occurs, a serious sequela such as quadriplegia could result. Care should be taken in performing the injection on a sedated patient or a patient with narrowed epidural space due to spinal stenosis or large central disc herniation. In dural puncture, an accompanying symptom could be a headache and the incidence is more frequent in lumbar than in cervical punctures. The epidural blood patch may be required depending on the severity of symptoms.

1.6 Transforaminal Approach and Selective Nerve Root Block (SNRB) In the transforaminal approach, compared to the interlaminar approach, the drug can be adequately spread to the ventral aspect of the epidural space as well as the area around the nerve root. It is thus superior for short-term relief of radicular pain by directly acting on the torn annulus with herniated disc and resulting in compressed and inflamed nerve [6, 7].

Fig. 5  Comparison of final position of needle in selective nerve root injection and transforaminal injection

The SNRB is a method of drug injection where the needle is positioned just lateral to the foramen and the contrast is subsequently spread only in the area around the nerve root. The method is widely used for diagnostic purposes. In the SNRB, the final position of the needle is the outside of the foramen to be distinguished from the transforaminal epidural block (Fig. 5). But as the two techniques are identical with respect to technical application, they will be discussed concomitantly.

280

1.6.1 Technique: Cervical Transforaminal Epidural Injection The patient is guided towards a supine position with a shoulder roll to have the cervical spine in extension. If the head of the patient is turned to the opposite side, locating the injection site could be facilitated. The C-arm in the PA state can be rotated in the 45–60° lateral oblique direction to allow adequate visualization of the neural foramen (Fig. 6). After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. To avoid the vertebral artery and exiting nerve root, the needle is advanced to the postero-­ inferior portion of the foramen as the target using the coaxial technique. The coaxial technique is the method of needle insertion after having aligned the needle axis to the C-arm axis. The needle is advanced in a slightly medial direction after touching the superior articular process, then it enters the foramen, at which point the needle is

Fig. 6  Right oblique view of cervical spine. Red curve: course of vertebral artery/white dash line: articular pillar of C6/black dash circle: contralateral pedicle

S. Yoo and J. T. Kim

advanced just 2–3 mm further. The medial location of the needle tip is checked on the C-arm PA image, then the epidural or perineural spread is checked through the injection of nonionic contrast, after which the medication can be injected. In selective nerve root block, the process is identical up to the needle being advanced to the postero-inferior portion of the foramen. The needle however is not advanced further after touching the superior articular process, while it is minutely adjusted during the injection of contrast to check the nerve root spread [14]. Due to the possibility of intravascular injection, particulate steroids should not be used; instead, dexamethasone sodium phosphate is used at 4–10 mg. If possible, the use of digital subtraction angiography to check intravascular spread upon the injection of contrast is recommended.

1.6.2 Technique: Lumbar Transforaminal Epidural Injection The patient is guided towards a prone position and the C-arm is rotated in the 20–30° ipsilateral oblique direction. After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. To avoid the spinal nerve, the needle is advanced in the superior aspect of the foramen, the inferior aspect of the pedicle, and the inferolateral aspect of the pars interarticularis. The inferolateral margin of the pars interarticularis is targeted as the needle is advanced using the coaxial technique (Fig. 7). If the needle touches the bone, the C-arm should be adjusted to the lateral position and the needle should be directed slightly towards the lateral side. The needle is then advanced in the anterior and superior aspects of the foramen. The patient complaining of paresthesia indicates the nerve root irritation, which requires the needle to be slightly withdrawn. After checking epidural and nerve root spread through the injection of 1–2 mL of nonionic contrast, the medication is injected. In selective nerve root block, the needle can be advanced in a less oblique direction, with the final position slightly on the exterior of the foramen. The contrast injection should show the spread of the contrast only at a single nerve root.

Spinal Blocks and Radiofrequency Techniques

a

281

b

Fig. 7  Oblique image (a) and AP image (b) of lumbar transforaminal injection. (a) Spinal needle is positioned beneath the inferolateral portion of pars articularis. Dotted line: margin of transverse procss-pars-inferior articular processes/ dash line: margin of superior articular process. (b) Epidural and perineural spread of contrast

a

b

c

Fig. 8  C-arm images of sacral transforaminal epidural block. (a) After aligning the axis with the sacral foramen by rotating

the C-arm, insert the needle coaxially. (b) Needle position in the lateral image. (c) Perineural spread of contrast

1.6.3 Technique: Sacral Transforaminal Epidural Injection As in the lumbar transforaminal block, the patient is guided towards a prone position and the C-arm in the AP position is rotated in approximately 5° ipsilateral oblique direction, then craniocaudally rotated until the sacral foramen is visible. After skin preparation and draping in a sterile manner, the skin is anesthetized. The needle is advanced so that it passes through the posterior aspect of the sacral fora-

men, then the C-arm is laterally rotated to check the needle depth with respect to the caudal ­epidural space. After the injection of contrast, the epidural/perineural spread is checked on both lateral and AP images, then the medication is injected (Fig. 8).

1.6.4 Complication of Transforaminal Approach The same potential complications as in the interlaminar epidural block could occur, including infection, bleeding, neurovascular complication,

S. Yoo and J. T. Kim

282

trauma to the spinal nerve, and intrathecal or subarachnoid injection. Particular care should be taken in the transforaminal approach regarding vascular complications. The trauma to the spinal segmental artery or the injection of particulate steroid could result in cord infarction. Notably, if the Adamkiewicz artery, the largest segmental artery, is affected, paraplegia could be induced. While the Adamkiewicz artery is located between T9 and L1 in 80% of cases, it may be found anywhere between T7 and L4. The risk is greater in the cervical transforaminal approach due to increased vasculature. In the case of intravascular injection to the vertebral artery, a serious result may occur; generalized seizure for the use of local anesthetics and cord infarction, brain infarction, or blindness for the use of the particulate steroid [15]. In cervical transforaminal injection therefore it is advisable not to use local anesthetics or particulate steroids.

2.2 Anatomy

The facet joint is the true joint with synovial lining and cartilaginous surface of superior articular process and inferior articular process. The capacity of the facet joint is 0.5–1  mL in the cervical spine and 1–1.5 mL in the lumbar spine [17]. The cervical facet joint forms a steep angle in the cephalad to caudal direction. This structure allows great amounts of rotation, flexion, and extension. The thoracic facet joint takes a vertical orientation, while the structure allows rotation-­free lateral flexion. The lumbar facet joint has a structure in which the inferior articular process in the anterolateral direction and superior articular process in the posteromedial direction are in an oblique orientation. This is advantageous in flexion, extension, and rotation although the ranges are smaller compared to the cervical region. The facet joint and joint capsule are inner2 Facet Injection vated through the medial branch of the primary dorsal rami [18]. The cervical and lumbar spinal 2.1 Introduction nerves are divided into the anterior rami and the posterior rami as they pass through the foramen. Osteoarthritis is a universal phenomenon of all The ventral rami include most of the motor and joints in the human body during aging. The spine sensory fibers of the corresponding level. The facet joint is not an exception. Facet arthritis pro- dorsal rami are once again divided into the latgresses as the axial loading on the facet joint eral, intermediate, and medial branches. The latincreases as a result of disc space narrowing eral and intermediate branches supply the caused by degenerative changes in the disc [16]. para-spinous musculature and longissimus musTypically, facet arthritic pain occurs as the axial cle, respectively. The medial branch, as it runs spinal pain at rest or worsens with forwarding above the base of the transverse process, joins flexion or rotation of the spine, which is not easy the superior articular process, and supplies to to differentiate from other causes such as SI joint the joints, multifidus, inter-spinal muscles, and pain or discogenic pain. In the past, the only ligaments as it thrusts along the articular available treatment for facet-related pain was to process. arrest the motion that may induce the pain via The cervical dorsal rami drive around and exit segmental fusion. the lateral aspect of the articular pillar and lamina Facet injection methods such as intra-articular (Fig. 9). The lumbar medial branch nerve passes facet block and medial bundle branch block above the base of the transverse process that joins (MBBB) may be useful in diagnosing facet-­ superior articular process, then drives along the related pain and alleviating acute pain. In addi- lateral aspect of the facet joint [19] (Fig. 10). The tion, long-term pain relief can be anticipated even lateral margin and transverse process base of the without surgery through the use of radiofre- articular pillar become the cervical and lumbar quency ablation (RFA). MBBB targets, respectively.

Spinal Blocks and Radiofrequency Techniques

283

C3

L3

C4

L4 Course of medial branch

C5

L5

S1 C6

Fig. 10  The lumbar medial branch runs past the boundary between superior articular process and transverse process and runs around the lateral aspect of the facet joint C7

injection and MBBB are used, and the latter is known to be more predictive [21]. However, in the case involving only a single facet joint or pain of recent onset, an intra-articular injection may still be a favorable choice.

2.4 Cervical Facet Injection Fig. 9  If the needle advances the midpoint between the superior and inferior articular processes, the midway of the anterior and posterior margin of the articular pillars as the target, it can be positioned in the medial branch

2.3 Indication and Contraindication While the treatment of pain due to facet arthritis begins with a conservative therapy such as drug or physical therapy, an intervention such as steroid injection or RFA may be applied if the conservative therapy is ineffective. Intra-articular facet injection and RFA are used for therapeutic purposes. The pain relief effect of intra-articular facet injection lasts for several days to weeks; that of RFA lasts for a minimum of 3 months, on the contrary [20]. For diagnostic purposes, IA

2.4.1 Cervical Intra-Articular Facet Injection The patient is guided towards a prone position with the head adjusted straight. The C-arm is rotated in approximately 25–35° caudal direction for the alignment to the facet joint axis. The cervical level is counted upwards from T1 for identification. After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. Targeting the facet joint space, a 22- or 25-gauge 3.5-inch spinal needle is advanced using the coaxial technique. When the needle touches the surface of the joint space, it is advanced slightly deeper to be positioned inside the joint capsule, while the lateral image is used for confirmation. As an abrasion on the articular

S. Yoo and J. T. Kim

284

a

b

Fig. 11  Target point of cervical medial branch block. (a) In the lateral image, the needle is placed in the center of the articular pillar. (b) While checking the PA image, place the needle on the lateral margin of the midlevel of articular pillar (waist)

surface could aggravate the pain, the needle should not be inserted too deep through the articular surface. After checking the accurate position on AP and lateral images, the medication is injected without the prior contrast injection. This is because the cervical facet joint is approximately 0.5 mL in volume so the use of contrast could limit the injectable volume of medication. Dexamethasone is recommended as it is safe to use nonparticulate steroids. Approximately 4  mg in total can be used in separate portions across all joints.

2.4.2 Cervical Medial Bundle Branch Block (MBBB) The cervical medial branch passes through the articular pillar located in the middle between the superior articular process and the inferior articular process. The region can be approached through posterior and lateral approaches. While the latter is known to lead to better outcomes [22], care should be taken as there is a possibility of cord injury through the unintended entry of the needle into the spinal canal. In the posterior approach, the patient is guided towards a prone position with a headrest. The C-arm is rotated in the 25–35° caudal direction to obtain in-line visualization of the facet joint and

the articular pillar. In the lateral approach, the patient is guided towards a lateral decubitus position with a pillow for support to allow the neck to be in a neutral position. The C-arm is adjusted so that the left and right articular pillars accurately overlap. After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. The target point is the lateral margin of the midlevel of an articular pillar (waist) for the PA image and the center of an articular pillar (trapezoid) for the lateral image (Fig. 11). The needle is inserted in the posterior approach, while the PA image is checked on the posterior, and the needle position is confirmed on the lateral image. The order is reversed in the lateral approach, i.e., the direction of needle insertion varies, but the final position of the needle tip is identical. A 22- or 25-gauge 3.5-inch spinal needle is positioned to the target point using the coaxial technique. After checking the needle position on the AP and lateral images, 0.5 mL of local anesthetics (2% lidocaine or 0.5% bupivacaine) per level is injected.

2.4.3 RFA of Cervical Medial Branch In the RFA, an RF cannula is required instead of a spinal needle. In the conventional RF treat-

Spinal Blocks and Radiofrequency Techniques

ment, a 10  cm SMK cannula with an attached 5 mm active tip is used in most patients except obese patients. The lesion can be formed only through the active tip. In positioning the cannulae, care should be taken to align the direction of the active tip and the direction of the target nerve. As in the posterior approach of MBB, the cannula is advanced to the lateral margin of the articular pillar. To align the shaft of the active tip and the course of the medial branch, the cannula should be advanced 2–3  mm further in lateral aspect along the bony margin. After the accurate positioning of the tip, the sensory-motor dissociation test is performed: the patient should report pain or tingling during stimulation at 50  Hz at (sensory threshold * 3) V or 3 V. While the position of the cannula is maintained, each level is anesthetized using 0.5 mL of 2% lidocaine. The lesion is formed at 80° for 60–90 s.

2.5 Lumbar Facet Injection 2.5.1 Lumbar Intra-Articular Facet Injection The patient is guided towards a prone position. The C-arm is rotated without caudal angulation in the 25–35° ipsilateral oblique direction. After skin preparation and draping in a sterile manner, the skin is anesthetized using 1% lidocaine. A 22or 25-gauge 3.5-inch spinal needle is advanced to the joint space using the coaxial technique (Fig. 12). As the needle touches the joint capsule, the lateral image is checked, and the needle is advanced slightly further until the needle tip is inside the joint space. The capacity of the lumbar facet is limited to approximately 1.5 mL, but it is safe to confirm the needle position by contrast injection. After confirming the joint space by contrast injection, the medication is injected. The 1:1 mixture of 80  mg of methylprednisolone and

285

Fig. 12 Target point of intra-articular injection and medial branch injection on oblique image of lumbar spine. Dotted rectangle: facet joint space/dashed circle: target point of medial branch block

0.5% bupivacaine is injected across all joints in separate portions.

2.5.2 Lumbar Medial Branch Block The medial branch nerve runs above the base of the transverse process that joins superior articular process [19]. The target of MBBB is the groove between the transverse process and superior articular process (Fig. 12). The patient is guided towards a prone position. The C-arm is rotated in the 25–35° ipsilateral oblique direction to allow all junctions of the transverse process and superior articular process as well as facet joint to be visualized. After skin preparation and draping in a sterile manner, the skin is anesthetized. A 22- or 25-gauge 3.5-inch spinal needle is advanced coaxially towards the base of transverse process base, where transverse process joins superior articular process. As the needle tip contacts the bone, the medication is injected to each level with 0.5 mL of local anesthetics.

S. Yoo and J. T. Kim

286

2.5.3 RFA of Lumbar Medial Branch The RFA is performed using a method similar to that of MBBB despite slight differences. The C-arm is rotated in the 25–35° ipsilateral oblique direction as well as in the 25–30° caudal direction. This is for confirming the alignment of the direction of the active tip with the course of the medial branch nerves. A 10 cm SMK cannula with a 5 mm active tip is used. Using the same method of MBBB, the cannula is advanced until it touches the transverse process base. To position the active tip on the course of the medial branch nerve, the cannula is advanced approximately 2–3 mm further along the superior margin of the transverse process. The lateral image is used to confirm that the tip is positioned on the superior articular process base, not entering the foramen. The sensory-motor dissociation test is performed: the patient should report pain or tingling during stimulation at 50  Hz at (sensory threshold *3) V or 3 V. While the position of the cannula is maintained, each level is anesthetized using 0.5 mL of 2% lidocaine. The lesion is formed at 80° for 60–90 s.

2.6 Complication of Facet Injections The potential complications of intra-articular facet injection include infection, transient increase in pain, and cord injury although they are reported to be rare. Nevertheless, for the injection to the cervical region, care should be taken as the leakage upon the injection of an excess amount of anesthetics can cause a complication due to the small volume of the facet joint. An overflow of anesthetics on the C3–C6 levels could cause phrenic nerve palsy. In the case of MBBB, the potential complications include infection and mild pain at the injection site although they are likewise rare. In the case of RFA, tissue destruction at the spinal nerve or cord may occur. As a preventive measure, pre-ablation physiologic testing is per-

formed. Some patients may complain of an increase in pain or hyperalgesia immediately after the surgery, but improvements within several days to weeks have been reported in most cases [20].

References 1. Evans W.  Intrasacral epidural injection in the treatment of sciatica. Lancet. 1930;216(5597):1225–9. 2. White AH. Injection techniques for the diagnosis and treatment of low back pain. Orthop Clin North Am. 1983;14(3):553–67. 3. Kobayashi S, Takeno K, Yayama T, et  al. Pathomechanisms of sciatica in lumbar disc herniation: effect of periradicular adhesive tissue on electrophysiological values by an intraoperative straight leg raising test. Spine (Phila Pa 1976). 2010;35(22):2004– 14. https://doi.org/10.1097/BRS.0b013e3181d4164d. 4. Davidson JT, Robin GC.  Epidural injections in the lumbosciatic syndrome. Br J Anaesth. 1961;33:595– 8. https://doi.org/10.1093/bja/33.11.595. 5. White AH, Derby R, Wynne G.  Epidural injections for the diagnosis and treatment of low-back pain. Spine (Phila Pa 1976). 1980;5(1):78–86. https://doi. org/10.1097/00007632-­198001000-­00014. 6. Manchikanti L.  Transforaminal lumbar epidural steroid injections. Pain Physician. 2000;3(4):374–98. 7. Schaufele MK, Hatch L, Jones W. Interlaminar versus transforaminal epidural injections for the treatment of symptomatic lumbar intervertebral disc herniations. Pain Physician. 2006;9(4):361–6. 8. Rathmell JP. Chap 5. Interlaminar epidural injection. In: Atlas of image-guided intervention in regional anesthesia and pain medicine. 2nd ed. Wolters Kluwer/Lippincott Williams & Wilkins Health; 2012. p. 34–63. 9. Alleyne CH Jr, Cawley CM, Shengelaia GG, Barrow DL.  Microsurgical anatomy of the artery of Adamkiewicz and its segmental artery. J Neurosurg. 1998;89(5):791–5. https://doi.org/10.3171/ jns.1998.89.5.0791. 10. Johansson A, Hao J, Sjolund B. Local corticosteroid application blocks transmission in normal nociceptive C-fibres. Acta Anaesthesiol Scand. 1990;34(5):335–8. https://doi.org/10.1111/j.1399-­6576.1990.tb03097.x. 11. Rathmell JP. Chap 4. Phamacology of agents used during image-guided injection. In: Atlas of image-guided intervention in regional anesthesia and pain medicine. 2nd ed. Wolters Kluwer/Lippincott Williams & Wilkins Health; 2012. p. 23–32. 12. Abrecht CR, Saba R, Greenberg P, Rathmell JP, Urman RD.  A contemporary medicolegal analysis of outpatient interventional pain procedures: 2009-­ 2016. Anesth Analg. 2019;129(1):255–62. https://doi. org/10.1213/ANE.0000000000004096.

Spinal Blocks and Radiofrequency Techniques 13. Bartynski WS, Grahovac SZ, Rothfus WE. Incorrect needle position during lumbar epidural steroid administration: inaccuracy of loss of air pressure resistance and requirement of fluoroscopy and epidurography during needle insertion. AJNR Am J Neuroradiol. 2005;26(3):502–5. 14. Pobiel RS, Schellhas KP, Eklund JA, et al. Selective cervical nerve root blockade: prospective study of immediate and longer term complications. AJNR Am J Neuroradiol. 2009;30(3):507–11. https://doi. org/10.3174/ajnr.A1415. 15. Rozin L, Rozin R, Koehler SA, et  al. Death during transforaminal epidural steroid nerve root block (C7) due to perforation of the left vertebral artery. Am J Forensic Med Pathol. 2003;24(4):351–5. https://doi. org/10.1097/01.paf.0000097790.45455.45. 16. Adams MA, Hutton WC.  The mechanical function of the lumbar apophyseal joints. Spine (Phila Pa 1976). 1983;8(3):327–30. https://doi. org/10.1097/00007632-­198304000-­00017. 17. Glover JR.  Arthrography of the joints of the lumbar vertebral arches. Orthop Clin North Am. 1977;8(1):37–42.

287 18. Groen GJ, Baljet B, Drukker J.  Nerves and nerve plexuses of the human vertebral column. Am J Anat. 1990;188(3):282–96. https://doi.org/10.1002/ aja.1001880307. 19. Shuang F, Hou S-X, Zhu J-L, et al. Clinical anatomy and measurement of the medial branch of the spinal dorsal ramus. Medicine. 2015;94(52):e2367. 20. Rathmell JP.  Chap 7. Facet injection: intra-articular injection, medial branch block, and radiofrequency treatment. In: Atlas of image-guided intervention in regional anesthesia and pain medicine. 2nd ed. Wolters Kluwer/Lippincott Williams & Wilkins Health; 2012. p. 80–117. 21. Cohen SP, Bhaskar A, Bhatia A, et  al. Consensus practice guidelines on interventions for lumbar facet joint pain from a multispecialty, international working group. Reg Anesth Pain Med. 2020;45(6):424–67. https://doi.org/10.1136/rapm-­2019-­101243. 22. Cheng J, Gutenberg L, Dalton J.  Comparative long-­ term outcomes of lateral versus posterior approach to cervical facet medial branch radiofrequency ablation [abstract# 179]. Pain Med. 2013;14:586.

Percutaneous Epidural Neuroplasty Seon-Jin Yoon and Dong Ah Shin

1 Introduction Percutaneous epidural neuroplasty (PEN) is a highly effective pain-relieving technique that can be employed to treat patients suffering from recurrent pain, even after they have undergone conservative treatment or conventional spinal injections [1–3]. PEN and its variations are available to physicians who understand adhesion-related pain [4, 5]. The primary objective of PEN is to restructure the epidural space by using mechanical maneuvers, hydrodissections, and chemical adhesiolysis to remove adhesions [2, 6]. The procedure can be completed within a day, or the treatment can be maintained for a more extended period [1]. It is worth noting that gross adhesions can be induced by spinal surgery and microscopic adhesions are found in patients with chronic pain or herniated intervertebral discs [5, 7, 8]. Similar to the restricted movement of frozen shoulder, epidural adhesion may limit the free movement of neural structure due to fibrosis [9]. Moreover, epidural adhesions can impede drug delivery to

target tissues [1]. PEN can effectively eliminate epidural adhesions, enabling improved drug spread and better outcome as compared to those who do not undergo adhesiolysis [10–14].

2 Classifications PEN can be classified based on the type of catheter used or if  epiduroscopy  is employed. Soft catheters are less painful, but they can be difficult to use. They are challenging for finding the target  locations and doing  advancement, steering, and mechanical adhesiolysis (Fig.  1). In contrast,  the  navigable steering catheters are relatively safe and easy to use because of their more rigid tip (Fig.  2). Balloon neuroplasty catheters can expand the narrowed epidural space by employing an elastic balloon [15–18]. Epiduroscopy allows for visualization of the intraluminal space of the spinal canal, and it may improve the outcome of PEN as direct visualization helps prevent injury to neurovascular structures [19].

S.-J. Yoon (*) · D. A. Shin Severance Hospital, Yonsei University, Seoul, Republic of Korea e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_26

289

S.-J. Yoon and D. A. Shin

290

a

2.5cm(~1 inch)

b

30°

Fig. 1  Tips for handling a soft catheter. (a) Bend the distal 1-inch part of the catheter at a 30° angle. (b) Tie a knot at the proximal end of the catheter, and by turning it left or

right, the bent tip of the catheter can be directed towards the target accordingly

Fig. 2  Tips for handling a navigable catheter. Dual direction lever is used to steer the tip of a catheter. This navigable catheter tip is advantageous for mechanical adhesiolysis, and the soft catheter tip allows entererance to the neural foramen with greater safety

Dual direction steering lever

3 Indications Indications for PEN include epidural adhesion-­ related pain syndromes, e.g., post-spinal surgery syndrome, spinal stenosis, and  herniated intervertebral discs [20]. Contraindications include medical and psychological aspects, such as infection, coagulopathy, anticoagulation, and adverse reactions to planned drugs or unreasonable patient expectations  on pain reduction. As PEN

Soft, steerable catheter

may not always be successful, patients need education or warning regarding the  expected outcomes and possible complications.

4 Preoperative Preparation To perform PEN procedure, informed consent must be obtained from the patient. The patient is then sedated with midazolam 1 h before the procedure [1]. Midazolam is contraindicated in

Percutaneous Epidural Neuroplasty

patients with a history of allergy, acute narrow-­ angle glaucoma, and hypotension. Side effects of midazolam are more common in older and sick patients. The procedure should be performed in a room where the Advanced Cardiovascular Life Support protocol is readily available. To properly respond to emergencies such as hypotension and arrhythmia, an intravenous line should be prepared in the patient’s arm. Electrocardiography, blood pressure, and oxygen saturation should be constantly monitored during the procedure.

5 Patient Positioning and Sacral Hiatus Puncture The patient should be placed on a radiolucent table in a prone position. In some cases, a caudal approach for back pain may require a pillow below a patient’s abdomen to stretch lumbar lordosis if it exists [18]. A sacral hiatus is then found by pressing the area and feeling elastic tension. The skin of the sacral hiatus should be widely disinfected with betadine, and a surgical drape should be placed to maintain a sterile field at the surgical site. The skin is then anesthetized by injecting 2% lidocaine (3 cc) into the lower margin of the sacral hiatus at a 20° downward angle. After puncture of the sacral hiatus, the epidural space is anesthetized with 2% lidocaine (2 cc), followed by a waiting period of several minutes during which lidocaine anesthetizes soft tissues. This waiting period allows for the preparation of other solutions required for later in the procedure. During the procedure, proper needle placement is critical to avoid complications such as bony puncture or bowel penetration. The needle tip should be located below the level of the S3 foramina, which corresponds to 1 cm above the sacral hiatus. To confirm proper needle placement, perform negative aspiration to rule out dural puncture or vascular injury.  To obtain an epidurogram with a contrast dye, take an AP view

291

using a mixture of omnipaque (4 cc) and 1% lidocaine (1 cc). Lidocaine can be used to reduce pain during catheter advancement and subsequent adhesiolysis. A caudal epidurogram can also be used to visualize the road map of the epidural space.

6 Catheter Advancement A PEN catheter is then inserted through a Tuohy needle. In the case of a soft catheter, the direction of the catheter can be adjusted by tip bending and knot steering (Fig. 1a). A knot is made in the proximal area of the catheter to allow for navigation and adhesiolysis  (Fig. 1b).  By turning the knot left or right, the bent tip of the soft catheter is directed toward the target point. The advantages of the soft catheter system include less dural tear risk, neural injury, vascular injury, and procedural pain; however, its driving force is technically demanding. Alternatively, navigation catheters are equipped with a lever that can steer the catheter tip. The advantage of a navigation catheter is that the direction of the catheter tip can be easily adjusted by turning the lever. Because the catheter is relatively rigid than soft catheters, it may be required in patients with severe adhesion (Fig. 2). Different techniques can be used to reach the ventral epidural space (Fig.  3a). Because the sacral roof is ovoid, when the catheter moves laterally, it moves naturally to the ventral side (Fig. 3b). If it passes through the ventral side of the exit root of the lower level, it easily arrives at the ventral epidural space (Fig. 3c). The catheter tip may cross or bypass a bulging disc to reach the ventral epidural space (Fig.  3d); a bulging intervertebral disc space may be a hurdle for a catheter, and bulging may be avoided by laterally shifting the catheter. In the lateral view, care must be taken to avoid puncturing the ventral dura with the catheter tip.

S.-J. Yoon and D. A. Shin

292

a Tuohy needle

Neuroplasty catheter

Sacral hiatus S1 nerve

b

L5 nerve

c

L4 nerve

d

Underneath the nerve

Fig. 3  Navigation technique to reach the ventral epidural space. (a) Schematic diagram. A Tuohy needle is inserted at the sacral hiatus. A catheter is inserted through the needle and advanced to the target. (b) The sacral roof is ovoid, so when the catheter moves laterally, it naturally goes to the ventral side. (c) At this time, if it passes

Turn around the protruding part

through the ventral side of the exit root of the lower level, it easily arrives in the ventral epidural space. (d) To reach the ventral epidural space, the catheter tip may cross or bypass the bulging disc. In the lateral view, care must be taken not to puncture the ventral dura with the catheter tip

7 Adhesiolysis After the tip of the catheter reaches the target (Fig. 4), an epidurogram is obtained with 2 cc of epidurogram solution (omnipaque 4  cc mixed with 1 cc of 1% lidocaine) to determine the adhesion status. The filling defect of the radiopaque dye may  indicates adhesion, and three types of adhesiolysis techniques can be applied: mechanical dissection, hydrodissection, and enzymatic digestion. An AP fluoroscopy view can be obtained during the gentle neuroplasty procedure. During the procedure, an epidurogram may also reveal adhesiolysis status. Patients should be monitored for pain and vital signs as severe pain-­ induced hypertension could occur during this procedure. If a balloon-inflatable catheter is used for lumbar spine diseases [18], the pressure effect of the balloon should be considered. During navigation, the balloon should be deflated, particu-

Inflammed DRG

Pain generating microadhesions

Fig. 4  Ideal location of the catheter tip. The tip is located on the ventral side of the dural sac and nerve root. A red swollen nerve root is attached to the underlying tissues by adhesion. After adhesiolysis, anti-inflammatory drugs may be injected into the treated area

Percutaneous Epidural Neuroplasty

293

larly inside the intervertebral foramen; a balloon needs at most 0.1 cc of contrast dye to reach its full expansion to a diameter of 10 mm. While the surgeon may not feel any resistance, the adjacent affected structures such as nerve roots may be severely compressed by the balloon; thus, slow expansion is required to prevent injury and avoid balloon rupture [18]. Furthermore, multiple cycles of balloon inflation need to be repeated (maximum of 5 s in expanded status) rather than continuous ballooning to prevent blockage of local blood circulation. Two types of solutions are injected after completion of neuroplasty or improvement of the filling defect. For adhesiolysis (neuroplasty solution), a mixed solution is prepared by mixing 0.2% ropivacaine (9  cc ropivacaine 40  mg/20  mL), hyaluronidase 3000  units (H-lase at 1500  units; 2 ampules), and tramadol 50 mg (tridol, 1 ampule). The solution should be stored in a 10-cc injectable syringe. After adhesiolysis (anti-­ inflammatory solution), 5 mg of dexamethasone (2 ampules for a total of 10 mg) should be prepared as a potential anti-inflammatory agent in a 10 cc syringe. Epidural bleeding occasionally occurs but rarely has fatal consequences. It may be managed with slow injection of normal saline. Elevated epidural pressure may prevent minor bleeding. If bleeding does not stop within approximately 10 min, hemostatic agents may be used. To prevent bleeding complications, PEN should be performed gently and should be avoided in contraindicated patients. In some cases, antiplatelet medications may be premedicated with reversing agents before PEN is performed [21]. At the end of the procedure, the catheter and needle are removed sequentially; if the catheter is stuck, it is removed to avoid a torn catheter remaining in the spinal canal [22–24]. Catheter cutting and needle breakage may be prevented by slow removal; a blood patch is not recommended.

relatively hard catheter is used, or if the catheter is advanced forcefully. When a dural tear occurs, there is no sudden resistance to catheter entry, and the patient complains of pain even with a small movement of the catheter tip. The cerebrospinal fluid will flow out from the catheter inlet; but if the dura is torn while the arachnoid is intact, cerebrospinal fluid may not leak out. If a dural tear is confirmed, drugs should not be injected. Injection of anesthetics (e.g., omnipaque mixed with lidocaine) can have disastrous results, such as seizures, unconsciousness, hypotension, cardiac arrest, arachnoiditis, or paralysis. Additionally, steroids or hyaluronidase may cause arachnoiditis. Nevertheless, if anesthetics are administered, cardiac resuscitation methods should be prepared, and the patient needs observation under monitoring and oxygen support. For monitoring, the patient should be rolled back to the supine position. Reverse Trendelenburg may help minimize upward diffusion or migration of injected anesthetics, and intravenous fluid loading may help in the treatment of hypotensive shock. Reports recommend intravenous lipid emulsion injections to scavenge overdosed anesthetics [25, 26]. If a dural tear is suspected, PEN should be stopped immediately and an epidurogram or myelogram pattern should be checked. A myelogram pattern typically shows that the dural sac is stained in the AP and lateral views, the cauda equina is visible, or it is stained as the fluid level pattern in the lateral view. In cases of subdural puncture, caution should be exercised, as they may look similar to the epidurogram pattern. The subdural puncture appears as a thinly layered contrast pattern on the ventral dura in the lateral view. While a soft catheter may not injure nerve roots directly during gentle manipulation, excessive movement or adhesiolysis may cause problems in the vascular and nervous systems.

8 Management of Dura Tears

9 Postoperative Management

Dura tears can occur incidentally during PEN, especially in elderly patients where the thin dura mater can be easily damaged. This may occur if a

Following PEN, the puncture site should be compressed to achieve better hemostasis, and a skin adhesive should be applied immediately to close

294

the puncture site. A bandage should then be placed for 1 day, and the patient should be monitored for approximately 30 min after the procedure. The patient could stay in the hospital ward for half a day and should be able to return to normal work or life activities 1 day after treatment. NSAID painkillers may be prescribed to reduce procedure-related pain; antibiotics are not required in patients without complications.

10 Conclusion PEN can effectively alleviate pain caused from adhesions by removing epidural scar tissues and administering drugs directly  to the affected target sites. When performed safely on appropriately selected patients, this procedure has the potential to provide significant relief from chronic pain.

References 1. Racz GB, Edward NC.  Techniques of neurolysis. Springer; 2016. 2. Manchikanti L, AD Kaye, Falco FJ, Hirsch JA: Essentials of interventional techniques in managing chronic pain. 2018. 3. Shin DA.  Endoscopic procedures on the spine. Springer; 2020. 4. CPT 2022 professional edition: American Medical Association. 2021. 5. Lee N, Ji GY, Yi S, Ha Y, Shin DA, Kim KN, Ha Y, Oh CH. Finite element analysis of the effect of epidural adhesions. Pain Physician. 2016;19(5):E787–93. 6. Raj PP, RG B.  Techniques of Neurolysis. Boston, MA: Springer US; 1989. 7. Ross JS, Robertson JT, Frederickson RC, Petrie JL, Obuchowski N, Modic MT, deTribolet N. Association between peridural scar and recurrent radicular pain after lumbar discectomy: magnetic resonance evaluation. Neurosurgery. 1996;38(4):855–61. discussion 861–853 8. Miyamoto H, Aoki M, Hidaka E, Fujimiya M, Uchiyama E.  Measurement of strain and tensile force of the supraspinatus tendon under conditions that simulates low angle isometric elevation of the Gleno-humeral joint: influence of adduction torque and joint positioning. Clin Biomech (Bristol, Avon). 2017;50:92–8. 9. Bosscher HA, Heavner JE. Incidence and severity of epidural fibrosis after back surgery: an endoscopic study. Pain Pract. 2010;10(1):18–24.

S.-J. Yoon and D. A. Shin 10. Manchikanti L, Pampati V, Fellows B, Rivera J, Beyer CD, Damron KS.  Role of one day epidural adhesiolysis in management of chronic low back pain: a randomized clinical trial. Pain Physician. 2001;4(2):153–66. 11. Manchikanti L, Singh V, Cash KA, Pampati V, Datta S.  A comparative effectiveness evaluation of percutaneous adhesiolysis and epidural steroid injections in managing lumbar post surgery syndrome: a randomized, equivalence controlled trial. Pain Physician. 2009;12(6):E355–68. 12. Manchikanti L, Rivera JJ, Pampati V, Damron KS, McManus CD, Brandon DE, Wilson SR.  One day lumbar epidural adhesiolysis and hypertonic saline neurolysis in treatment of chronic low back pain: a randomized, double-blind trial. Pain Physician. 2004;7(2):177–86. 13. Manchikanti L, Cash KA, McManus CD, Pampati V, Singh V, Benyamin R.  The preliminary results of a comparative effectiveness evaluation of adhesiolysis and caudal epidural injections in managing chronic low back pain secondary to spinal stenosis: a randomized, equivalence controlled trial. Pain Physician. 2009;12(6):E341–54. 14. Ji GY, Oh CH, Won KS, Han IB, Ha Y, Shin DA, Kim KN.  Randomized controlled study of percutaneous epidural Neuroplasty using Racz catheter and epidural steroid injection in cervical disc disease. Pain Physician. 2016;19(2):39–48. 15. Choi SS, Joo EY, Hwang BS, Lee JH, Lee G, Suh JH, Leem JG, Shin JW. A novel balloon-inflatable catheter for percutaneous epidural adhesiolysis and decompression. Korean J Pain. 2014;27(2):178–85. 16. Shin JW.  Methods for Executing the ZiNeu Series Catheter Procedure. In: Shin JW, editor. Spinal Epidural Balloon Decompression and Adhesiolysis. Singapore: Springer Singapore; 2021. p. 55–100. 17. Oh Y, Shin D, Kim D, Cho W, Na T, Leem J-G, Shin J-W, Kim D-H, Hahm K-D, Choi S-S. Effectiveness of and factors associated with balloon Adhesiolysis in patients with lumbar post-laminectomy syndrome: a retrospective study. J Clin Med. 2020;9:1144. 18. Shin JW. Spinal epidural balloon decompression and adhesiolysis. [S.l.]. Singapore: Springer Verlag; 2021. 19. Moon BJ, Yi S, Ha Y, Kim KN, Yoon DH, Shin DA.  Clinical efficacy and safety of trans-sacral Epiduroscopic laser decompression compared to percutaneous epidural Neuroplasty. Pain Res Manag. 2019;2019:2893460. 20. Cho PG, Ji GY, Yoon YS, Shin DA. Clinical effectiveness of percutaneous epidural Neuroplasty according to the type of single-level lumbar disc herniation: a 12-month follow-up study. J Korean Neurosurg Soc. 2019;62(6):681–90. 21. Park JH, Ahn Y, Choi BS, Choi KT, Lee K, Kim SH, Roh SW.  Antithrombotic effects of aspirin on 1- or 2-level lumbar spinal fusion surgery: a comparison between 2 groups discontinuing aspirin use before and after 7 days prior to surgery. Spine (Phila Pa 1976). 2013;38(18):1561–5.

Percutaneous Epidural Neuroplasty 22. Manchikanti L, Bakhit CE.  Removal of a torn Racz catheter from lumbar epidural space. Reg Anesth. 1997;22(6):579–81. 23. Kim TH, Shin JJ, Lee WY.  Surgical treatment of a broken neuroplasty catheter in the epidural space: a case report. J Med Case Rep. 2016;10(1):277. 24. Kang JH, Choi H, Kim JS, Lee MK, Park HJ.  A sheared Racz catheter in cervical epidural space for

295 thirty months: a case report. Korean J Anesthesiol. 2015;68(2):196–9. 25. Felice K, Schumann H. Intravenous lipid emulsion for local anesthetic toxicity: a review of the literature. J Med Toxicol. 2008;4(3):184–91. 26. Ok SH, Hong JM, Lee SH, Sohn JT. Lipid emulsion for treating local anesthetic systemic toxicity. Int J Med Sci. 2018;15(7):713–22.

Percutaneous Transforaminal Annuloplasty Shih-Min Lee

1 Introduction Chronic low back pain is the second most common cause of consulting with healthcare providers (HCP) around the world. Without proper treatment for this suffering, the economic and psychological impact on individuals and society is devastatingly bad [1]. Multiple biomechanical etiologies for low back pain have been suggested in the literature such as degenerative disc disease, annular fissures, compressive herniated nucleus pulposus, and facet arthropathy [2–5]. As can be seen, the pathophysiology of discogenic back pain is the growth of granulation tissue into the disc space through annular defects (fissure, cleft, and tear) resulting from degenerative disease or trauma.

Granulation tissue causes angiogenesis and chronic inflammatory processes in the disc that irritate free nerve endings in this area [6, 7]. Growth factors, including transforming growth factor-beta 1 and basic fibroblast growth factor, mast cells, and macrophages may also play a key role in the repair of the injured annulus fibrosus and subsequent disc degeneration [8]. It is notable that patients with this “intra-annular granulation” status (Fig. 1) have back pain rather than leg pain. Although the general course of discogenic pain is controversial, it is known that the pain is caused by destruction inside the disc, degenerative changes in the disc, and damage to the annulus. Percutaneous transforaminal annuloplasty to cauterize the granulation tissue is associated with the damaged annulus.

Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/978-­981-­19-­9849-­2_27. S.-M. Lee (*) Department of Neurosurgery, Cheongdam Wooridul Hospital, Seoul, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_27

297

S.-M. Lee

298

Fig. 1  Intra-annular granulation tissue syndrome, granulation tissue observed (white arrows) in disc with annular tear (courtesy of Dr. Wolfgang Rauschning, Academic University Hospital, Uppsala, Sweden). The nucleus pulposus flowing from the torn annulus fibrosus is not absorbed and grows into granulation tissue that includes blood vessels and nerves over several years and causes pain

2 Diagnosis It is no exaggeration to say that the key to this treatment lies in the diagnosis because discogenic back pain is difficult to diagnose accurately. In particular, it is important to identify the exact cause and select patients who will definitely benefit from percutaneous transforaminal annuloplasty. The most important thing in diagnosis is the patient’s clinical symptoms. The clinical symptoms of discogenic back pain include discomfort in sitting (sitting intolerance), difficulty lifting heavy objects, holding an extension, increased pain after hard work, and loss of ability to maintain posture for 30 min. Most of these symptoms are complex and nonspecific [9] (Table 1). MRI and Provocative discography are very important diagnostic tools for discogenic low back pain. MRI findings can be seen as follows,

Table 1  Diagnostic tools of discogenic back pain Diagnostic tool Clinical symptoms

MRI

Provocative discography

Positive finding Sitting intolerance Difficulty lifting heavy objects Extension catch Increased pain after a hard working day Cannot maintain posture over 30 min Annular defect with both T1 and T2 image Thickening of posterior annulus HIZ on T2 Positive with sharp, shooting pain

annular defect on both T1 and T2, and it can show thickening of the posterior portion of the annulus and the disc trapped inside the defect. The high-intensity zone is also a helpful finding in T2 MRI (Fig. 2). Invasive provocative discography is performed if the patient’s clinical features and MRI results are consistent with

Percutaneous Transforaminal Annuloplasty

299

Fig. 2  The high-­intensity zone (HIZ) is shown at the L4–5 level

discogenic back pain. If there is a defect or tear in the posterior annulus, contrast leakage can be seen in real time during discography. In addition, as the intradiscal pressure increases, nerve ending is stimulated, causing pain at the pathologic level.

3 Indications Since there are many causes of discogenic back pain, there is still controversy about which procedure is better for treating discogenic back pain, but the general relative indications for surgery include: • Clinical symptoms of discogenic back pain. • High-intensity zone (HIZ) on magnetic resonance imaging (MRI). • Positive sign in provocative discography.

• • • • • •

Fig. 3  Sinuvertebral nerve (dorsal aspects of intervertebral disc area include sensory nerve ending, red arrow)

4 Surgical Technique

Contraindications are as follows:

4.1 Step 1. Set up

Calcified disc. Severe stenosis. Segmental instability. Disc herniation. Infection. Tumor.

4.1.1 Instrument Target for the annuloplasty is sinuvertebral nerve ending into an annular tear that can ablate annulus. (Fig.  3) Transforaminal annuloplasty uses a side-firing laser (Ho:YAG) and it can cure the pathologic region accurately and

S.-M. Lee

300

safely. The flexible endoscopic Ho: YAG laser has a very small diameter and the length of the laser tip can also be actively adjusted (Figs. 4 and 5). It can be flexibly adjusted even in a very small space, and it enables treatment by targeting the desired l­ocation. If your hospital does not have the same instrument, we recom-

mend using the smallest endoscopic instrument you have. Instruments are as follows: • 18-gauge needle and guidewire • Sheath and dilator. • Scope with built-in fiber optics and Ho: YAG laser.

Fig. 4 Laser-assisted spinal endoscopy set; LASE®, CLAUS medical, USA. ((a) Laser line. (b) Endoscopic line. (c) Irrigation line)

4.1.2 Position and Anesthesia Before performing percutaneous transforaminal annuloplasty, it is important to know how to set up the operating room. The surgeon should always be on the symptomatic side, if the patient’s symptom is a central lesion, stand on the surgeon’s comfortable side, and the intraoperative image intensifier during surgery should be on the contralateral side. Make sure the patient is comfortable and prepare for anesthesia (Fig. 6). Conscious sedation with a benzodiazepine (Midazolam) and topical anesthesia with skin infiltration of 2–3 mL of 0.5–1% lidocaine and 6–8  mL of paraspinal muscle infiltration is recommended. The most painful points of the procedure are skin entry and annulus penetration; Therefore, it is recommended to inject an additional 2–3  mL of 0.5–1% lidocaine just before piercing the annulus. This will be enough to minimize pain. In perineural anesthesia, higher concentrations (e.g., 2% lidocaine) can paralyze motor function. When it occurs, confusion can arise whether this is a lidocaine side effect or a direct mechanical injury (Fig. 7a, b).

Image fiber Illumination fiber Laser fiber

Irrigation

Fig. 5  Tip of the flexible Ho:YAG laser scope, The laser tip can be lengthened and reduced by 1–5 mm

Percutaneous Transforaminal Annuloplasty

301

Fig. 6  C-arm on the opposite side of the surgeon and the scrub nurse stands on the right side

a

b

d

Fig. 7 (a–c) Schematic representation of the location of working cannula within annulus pulposus, Needle was placed in the posterior annulus. (d–i) Schematic represen-

c

e

tation of transforaminal endoscopic laser annuloplasty. The laser tip coming out and landing on the annulus (white arrow, I)

S.-M. Lee

302

f

g

h

i

Fig. 27.7 (continued)

4.2 Step 2. Landing of the Working Sheath (as Shallow as Possible) Provocative discography is performed prior to annuloplasty. It was performed with manual injection of indigo carmine, contrast, and normal saline solution in a 2:1:2 ratio. It can be checked for leakage of contrast through annular tear and positive provocation test. The procedure was canceled if there was no concordant pain or annular tear in fluoroscopy (Fig. 7c, d). Because the target is the ingrowth annulus, not the nucleus pulposus, the access pathway should be made shallower, and it is recommended to start it laterally to 1  cm more than the conven-

tional transforaminal procedure. Therefore, a typical skin entry point is 12–15 cm lateral to the midline. The needle was on a trajectory that approached the facet joint, and the usual axial angle of the needle was below 22° so as not to touch the anterior and central nucleus. Discography is done after needle insertion, followed by guidewire insertion through the needle. Skin incision is needed before putting in the working sheath. The guidewire is inserted to establish a working sheath for the endoscope under intraoperative image guidance. After the sheath passes the medial pedicular border, gentle hammering is possible to reach the point just past the midline. During working sheath insertion, make sure the bevel is facing dorsally (Fig. 7e–i).

Percutaneous Transforaminal Annuloplasty

4.3 Step 3. Annuloplasty After the proper working sheath is established, the posterior wall of the annular has been reached. Annular defects may be found and some entrapped nucleus pulposus stained with indigo carmine may be visualized inside the defect. At this point, because discogenic back pain is the result of inflammation and granulation tissue ingrowth, intradiscal vascularization and bleeding can be seen. After identification of the annular defect and trapped disc material, the disc is removed using endoscopic forceps. After the disc is removed, annuloplasty is done using the side-­firing Ho:YAG laser and radiofrequency (RF) bipolar cautery (Fig. 8). Finally, if needed, the traversing root and epidural space can be

303

visualized by endoscope.

gradually

withdrawing

the

5 Case Illustration A 30-year-old female patient was unable to drive for more than 30 min due to a pain in her back when sitting for a long time. She had been suffering from severe back pain two or three times a year. She traveled to several hospitals in the United States and tried oriental medical treatment or pain injection treatment, but the effect was only for a while. Discectomy was recommended at the university hospital. She visited our hospital and confirmed the L4–5 high-intensity zone (HIZ) on MRI (Fig.  9a).

a

b

Fig. 8  Disc is removed using endoscopic forceps (a), and cauterization by a bipolar (b)

S.-M. Lee

304

a

b

c

Fig. 9 (a) L4–5 high-intensity zone (HIZ) on Preoperative T2 MRI. (b) High-­intensity zone (HIZ) and bulging disc were removed on Postoperative MRI. (c) The working sheath in the posterior rim of the annulus was confirmed by lateral C-arm fluoroscopic view

Percutaneous Transforaminal Annuloplasty

305

Fig. 10  Endoscopic view of inflamed nuclear material dyed blue with indigo carmine. While the laser is being used, the area around it is red

Transforaminal annuloplasty was performed under conscious anesthesia. The working sheath in the posterior rim of the annulus was confirmed by lateral C-arm fluoroscopic view (Fig. 9c). Laser ablation of the interposed granulation and nucleus pulposus were performed through the annular puncture (Ho:YAG laser with side-firing fiber side, set at 2.5–10  W) (Fig. 10). The nucleus flowed through the annular tears, which lasted for a long time and became a scar. It was transformed into calluses (Video 1). Her treatment ended safely, and after rehabilitation, she successfully returned to work.

6 Complication Avoidance Mechanical complications, such as nerve damage due to incorrect needle insertion, allow the surgeon to directly assess and avoid the patient’s neurological changes because the patient remains conscious during the procedure. Unlike other endoscopic procedures, the diameter of the can-

nula is very small and the flow rate is low, so there is very little chance of headache and neck pain due to increased intracranial pressure. Dural tear is possible but is rarely seen in this procedure because the tip of the cannula is anchored in the annulus and epidural content does not need to be visualized. And since continuous intraoperative irrigation with antibiotic-infused saline was used during the procedure, there has been no surgical infection so far.

7 Summary Percutaneous transforaminal annuloplasty is an alternative treatment option for carefully selected patients with low back pain of discogenic origin. It has the benefit of visualization of intradiscal pathology and removal of the entrapped fragment which is the main cause of chronic inflammation leading to discogenic back pain. If inflammation and intradiscal bleeding are observed during the procedure, we can confirm that the patient will improve after the procedure.

306

References 1. Park CH, Lee KK, Lee SH. Efficacy of transforaminal laser annuloplasty versus intradiscal radiofrequency annuloplasty for discogenic low back pain. Korean J Pain. 2019;32(2):113–9. 2. Bogduk N, Windsor M, Inglis A.  The innervation of the cervical intervertebral discs. Spine (Phila Pa 1976). 1988;13:2–8. 3. Malinsky J.  The ontogenetic development of nerve terminations in the intervertebral discs of man. (histology of intervertebral discs, 11th communication). Acta Anat (Basel). 1959;38:96–113. 4. Groen GJ, Baljet B, Drukker J.  Nerves and nerve plexuses of the human vertebral column. Am J Anat. 1990;188:282–96. 5. Yoshizawa H, O'Brien JP, Smith WT, Trumper M. The neuropathology of intervertebral discs removed for low-back pain. J Pathol. 1980;132:95–104.

S.-M. Lee 6. Saal JA, Saal JS. Intradiscal electrothermal treatment for chronic discogenic low back pain: prospective outcome study with a minimum 2-year follow-up. Spine. 2002;27(9):966–73. 7. Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am. 1999;81(7):958–65. 8. Peng B, Hao J, Hou S, et al. Possible pathogenesis of painful intervertebral disc degeneration. Spine (Phila Pa 1976). 2006;31:560–6. 9. Lee SH, Kang HS.  Percutaneous endoscopic laser annuloplasty for discogenic low back pain. World Neurosurg. 2010;73(3):198–206.

SELD, Trans Sacral Epiduroscopic Lumbar Decompression Kang Taek Lim

1 Introduction

Flexible epiduroscopy and steerable surgical instruments can access the lesion through the Epiduroscopy is a flexible 0.9 mm diameter fiber- sacral hiatus, can permit direct visualization of optic spinal endoscope that can be inserted into lumbar epidural lesions, and is possible to the epidural space through sacral hiatus. decompress surrounding structures with miniIn 1996, the United States FDA (Food and mal impact on the patient’s musculoskeletal Drug Administration) approved the use of structures. Myelotec Myeloscopy (Myelotec, Inc., Great The recommended indications of this proceNeck, NY) epiduroscopy to visualize the epidural dure are back pain and radiculopathy that is space. refractory to conservative management with eviRuetten reported on the clinical application of dence of MRI imaging. epiduroscopically assisted laser therapy for post-­ In case of chronic lumbar pain after spinal surnucleotomy syndrome in 1997. Since then, there gery, spinal stenosis, and epidural fibrosis has has been considerable progress in the theoretical been implicated in the etiology of persistent pain, background for epiduroscopic diagnoses and which results from restricted movement, pressure treatment of lumbar lesions using a laser as a sur- on a nerve, or obstruction [2]. gical alternative to the traditional open surgery This epidurosopic procedure is to break up the for lumbar pathology [1]. scar tissue with mechanical adhesiolysis, and cut-

K. T. Lim (*) Seoul Segyero Hospital, Seoul, Republic of Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_28

307

K. T. Lim

308

a

b

c

Fig. 1 (a) Catheter. (b) Epiduroscope. (c) Flexible forceps

ting fibrosis with laser between neural structure and epidural space thus relieving the pain. For patients with chronic refractory low back, and/or lower extremity pain that could not be resolved with other conservative treatments, the epiduroscopic procedure has been introduced to many papers that show good results [3, 4]. In case of herniated disc, small size that can compress neural structure, and migrated disc is recommended, but huge ruptured disc is not recommended that is because procedures are difficult to get rid of the whole herniated fragment and can induce a recurrence of disc. In this chapter, we hope to introduce the epiduroscopic procedure as one of the effective therapeutic modalities for decompression of epidural space in symptomatic pathology.

2 Surgical Instruments The 3.0  mm diameter steerable catheter (VGC 3.0  mm, Myelotec, Inc., Roswell, GA) has 1.3 mm diameter two lumens (Fig. 1a), one hole is for inserting 0.9 mm diameter 1.5 K pixel flexible fiber optic endoscope (3000E, Myelotec, Inc., Roswell, GA) (Fig. 1b), and the other is for inserting instruments like laser fiber and forceps (Fig. 1c).

When the catheter is inserted into the sacral epidural space, the two holes are positioned up and down. The instrument and laser are inserted into the lower hole and the epiduroscopy is inserted into the upper hole to monitor the ­instrument’s movement and actions around neural tissues (Fig. 2a, b). Holmium: yttrium-aluminium-garnet (Ho: YAG) laser (Versa-PulseP20; Lumenis, Yokneam, Israel) with a 2.3F outer diameter end-firing fiber was used for this procedure (Fig.  2c). This Ho:YAG laser is pulsed laser designed for emitting light at 2100  nm in the near-infrared region of the electromagnetic spectrum [5], and has good visibility in the surgical field because the green aiming beam is easy to see against the vascular tissue surface and operating environment. The Ho:YAG laser has high water absorption, and, given, that water constitutes the majority of tissue, a substantial part of holmium energy is superficially absorbed. As a result, only superficial cutting, ablating, vaporization, and coagulation can be performed with an optical penetration depth of about 400  μm, which is comparatively safe in laserinduced thermal damage [5]. If adhesion scar needs to be physically removed, it can be removed using 1.2 mm diameter flexible forceps and it can also be used for biopsy in epidural space (Fig. 2d).

SELD, Trans Sacral Epiduroscopic Lumbar Decompression

309

a

b

c

d

Fig. 2 (a) A two-lumen of catheter. (b) The cross-section of catheter, upper hole for epidoroscope, lower hole for laser and forceps. (c) 2.3 F diameter laser fiber. (d) Bidirectional jaws forceps

3 Surgical Procedures The epiduroscopic procedure is performed under local anesthesia, in a prone position with the lumbo-sacrum slightly flexed to reduce lumbar lordosis. By reducing lumbar lordosis, the catheter passes easily through the lumbosacral area (Fig. 3). The sacral hiatus can be touched using left thumb and possible to confirm the location of sacral hiatus using C-arm lateral view. After local

Fig. 3  The lordosis angle must be reduced in order for the catheter to pass well through the ventral epidural space of lumbosacral area

K. T. Lim

310

a

b

Fig. 4  The catheter can be inserted into the ventral epidural space through sacral hiatus. (a) Catheter insertion. (b) Dummy practice

Fig. 5  The catheter is placed at the surgical site in the ventral epidural space

anesthesia around the sacral hiatus, a 5 mm-sized skin incision was made on the sacral hiatus, followed by a sacrococcygeal ligament puncture using the Tuohy needle under fluoroscopic guidance, to confirm properly inserted into the sacral hiatus (Figs. 4, 5). Then 1.5 mm diameter plastic cannula can be inserted through the Tuohy needle, and the catheter can be placed in ventral epidural space through plastic cannula. It is necessary to ensure that the catheter is well inserted into the ventral epidural space and

passes well to the destination, which can be verified through epiduroscopy to see ventral space anatomy and can be reconfirmed using the C-arm view (Fig. 5). When the catheter is inserted into the sacral epidural space, the two holes are positioned up and down. The instrument and laser are inserted into the lower hole, the epiduroscopy is inserted into the upper hole to monitor the instrument’s actions. After the endoscope is inserted into the catheter, lens should be washed with irrigation water so

SELD, Trans Sacral Epiduroscopic Lumbar Decompression

that the anatomy of epidural space can be seen well. The amount of water used in 1 h should not exceed 200 cc, If the amount of water used is more than 200 cc, the increased pressure on the epidural space can cause the patient to complain of neck pain and headache, nausea during the procedures. The catheter was administrated up to the level of the migrated disc in the anterior epidural space. The catheter was administrated up to the level of the lesions in the ventral epidural space. If the adhesions are identified by an endoscope, direct mechanical adhesiolysis is attempted with a steerable catheter to remove bands of scar tissues, between the neural structures and the lesion. At this time, it should be closely monitored with an endoscope to avoid

311

the occurrence of root damage due to severe compression of the root by the catheter (Fig. 6). If the adhesiolysis is not well solved by mechanical try, a laser is used to cut the fibrosis between the annulus and the root, which can be observed cutting fibrosis and shrink of annulus by the heat of the laser (Fig. 6d, Fig. 7). During the endoscopic procedures, surgeon can immediately see that the nerve roots are detached from adhesion scar and move freely. The annulus can confirm that it becomes a shrinkage under the endoscopic view and C-arm (Fig. 8), but in the immediate postoperative MRI, the objective degree of decompression may be less [6] (Fig. 9).

a

b

c

d

Fig. 6 (a) Surgical type adhesion scar. (b) Nonsurgical type adhesions. (c) Mechanical adhesiolysis using catheter. (d) Cutting adhesion band and shrinkage of annulus using laser

K. T. Lim

312

a

b

Fig. 7  Laser firing to cut fibrosis in epidural space. (a) Laser located at 6 o’clock position, (b) Epiduroscopic view during laser firing

a

b

c

d

Fig. 8 (a) Epiduroscopic view shows annulus compress nerve root, before procedures. (b) The final stage of the procedure, the space, between root and annulus created after shrinkage of annulus. (c, d) C-arm view of before and after decompression. White arrow indicates surgical site

SELD, Trans Sacral Epiduroscopic Lumbar Decompression

313

a

b

c

d

Fig. 9 (a, c) Preoperative sagittal and axial MRI. (b, d) Postoperative MRI

The HIZ (High-Intensity Zone) of lumbar intervertebral disc is a high-intensity signal located in the posterior annulus fibrosus on T2-weighted magnetic resonance images. It has a strong correlation between annular HIZ and the results of provocative discography in patients with low back pain (LBP) [7]. Like HIZ, discal

cysts, which contain a lot of water composition in a thin membrane, removing these lesions using laser is very effective (Figs. 10 and 11). Flexible forceps can be used to eliminate fibrosis more actively, and it can be used for tissue biopsy. At this time, care should be taken not to bite the nerve tissue (Fig. 12).

K. T. Lim

314

a

c

b

e

d

g

f

Fig. 10  HIZ at L45. (a, b): Preoperative. (c, d) Postoperative sagittal and axial MRI. (e) Before laser firing, thin HIZ membrane compress the neural tissue. (f, g) Epiduroscopic view shows removal of HIZ with laser firing

a

b

c

d

Fig. 11 (a, c): Preoperative MRI shows discal cyst. (b, d) Postoperative MRI

SELD, Trans Sacral Epiduroscopic Lumbar Decompression

a

315

b

c

Fig. 12 (a) The white arrow indicates bidirectional grasp jaws of forceps. (b) Forceps under epiduroscopic view. (c) Biopsy using forceps

4 Discussion The concept of the epiduroscopic procedure is to remove the fibrosis, adhesion, and granulation tissue by using a flexible steerable catheter and flexible instrument, which is to cut the fibrosis and shrinkage anulus by a using laser while looking directly at it with epidurocopy. Compared to procedures that do adhesiolysis with only a catheter, the procedures with the addition of an epiduroscopy allow surgical lesions observation leading to safer and more effective outcomes. The use of water is another aspect of this surgery, when water is injected into the ventral epidural space to get a good view of the lesion surface with an endoscope, the ventral epidural space can be better observed because the space between the dura and the annulus becomes wider due to water volume. The catheter can move from side to side, allowing it to move closer to the lesion and it is possible to visually diagnose which part of the

neural tissue is stuck to epidural structures in more detail by epiduroscopy. The mechanisms to eliminate pain in this procedure are to remove the adhesion, fibrosis, and granulation tissue with a catheter to separate the nerve from around the surrounding tissue [8], and the sinuvertebral nerve that causes the pain can be burned with a laser. It is also possible to induce decompression by applying heat to the nerve-­ surrounding tissues using a laser to shrink and to destruct the adhesion fiber around nerve root) [9–11] (Fig. 13). According to recent papers regarding the clinical outcome of this procedure for disc herniation have reported that the clinical outcome was favorable as there was a significant improvement in low back pain or radiating leg pain, low rates of surgical failure, or recurrence [12, 13]. During this process, if the catheter causes pressure on the nerves, nerve damage may occur, so be careful and take a good look at the patient’s condition, so communication with the patient

K. T. Lim

316

a

b

c

Fig. 13  Adhesiolysis process. (a) Approach the lesion, mechanical detachment using catheter. (b) Cutting of adhesion band using laser. (c) Final stage, shrinkage of annulus

during the procedure is important and keeping a close eye on the patient’s response is a way to prevent postoperative complications. Since the epidural venous complexes are formed a lot around the lesion, epidural bleeding may occur on the process of removing adhesion. Bleeding control is needed to prevent hematoma after surgery. With epiduroscopy, surgeon can find bleeding sites and can do hemostasis with laser coagulation effects. Epiduroscopic procedure showed rapid improvement of back pain and radiculopathy in outcomes between preoperative and postoperative data in the study. Ascher and Heppner used CO2 and Nd lasers to remove a small volume of tissue from the disc causing a corresponding decrease in the intradiscal pressure, which produced good results for improving back pain in 1984 [14]. As technology advanced, HO YAG lasers with short wavelengths and short tissue penetration depth were introduced into spinal surgery and promotes safety and effectiveness. In general, laser has an effect on the destruction of soft tissue results by cutting, vaporizing, ablating, and welding tissue. During this process, laser-induced heat is transferred to the irradiated tissues, resulting in shrinkage of annulus by laser-induced protein denaturation [15, 16]. Water irrigation for washing lens allowed direct visualization of the epidural space to monitor the whole process through epiduroscopy can prevent the thermal damage of nerve tissue induced by using laser [17, 18]. It is important to look at the patient’s reaction during laser firing because when the laser-­ induced heating reaches the neural structures, the patient complains of pain.

The final step of this procedure is to apply an anti-adhesive agent into the epidural space to prevent postsurgical adhesion [19, 20].

5 Conclusion An epiduroscopy is one of the MIS procedures that can easily reach the ventral epidural space easily through sacral hiatus. Surgical or nonsurgical type adhesion can be diagnosed by looking directly through epiduroscopy, and fibrosis can be removed by inserting instruments. Thanks to the development of epiduroscopic systems, various instruments can be inserted through the catheter, which makes it possible to perform various procedures in epidural cavity. At the moment, we could put a laser, forceps only, but in the future, if we can put in a flexible drill or side firing laser, several instruments, the surgical area of the epidurosopy will be enlarged.

References 1. Ruetten S, Meyer O, Godolias G.  Application of holmium:YAG laser in epiduroscopy: extended practicabilities in the treatment of chronic back pain syndrome. J Clin Laser Med Surg. 2002;20(4):203–6. 2. Guner D, Asik I, Ozgencil GE, Peker E, Erden MI. The correlation of epidural fibrosis with epiduroscopic and radiologic imaging for chronic pain after back surgery. Pain Physician. 2021;24(8):E1219–26. 3. Son S, Lee SG, Ahn Y, Kim WK. Clinical outcomes of trans-sacral epiduroscopic laser decompression (seld) in patients with lumbar disc herniation. Pain Res Manag. 2020;2020:1537875. Published online 2020 Jun 1 4. Jo DH, Yang HJ.  The survey of the patient received the epiduroscopic laser neural decompression. Korean J Pain. 2013;26:27–31.

SELD, Trans Sacral Epiduroscopic Lumbar Decompression 5. Sandhu AS, Srivastava A, Madhusoodanan P, et  al. Holmium: YAG laser for intra corporeal lithotripsy. Med J Armed Forces India. 2007;63(1):48–51. 6. Hazer DB, Acarbaş A, Rosberg HE. The outcome of epiduroscopy treatment in patients with chronic low back pain and radicular pain, operated or non-­operated for lumbar disc herniation: a retrospective study in 88 patients. Korean J Pain. 2018;31(2):109–15. 7. Aprill C, Bogduk N. High-intensity zone: a diagnostic sign of painful lumbar disc on magnetic resonance imaging. Br J Radiol. 1992;65:361–9. 8. Lee SH, Lee S-H, Lim KT.  Trans-sacral epiduroscopic laser decompression for symptomatic lumbar disc herniation: a preliminary case series. Photomed Laser Surg. 2016;34(3):121–9. 9. Park CH.  Efficacy of transforaminal laser annuloplasty versus intradiscal radiofrequency a­ nnuloplasty for discogenic low back pain. Korean J Pain. 2019;32(2):113–9. 10. Kim HS, Paudel B, Chung SK, Jang JS, Oh SH, Jang IT.  Transforaminal epiduroscopic laser ablation of sinuvertebral nerve in patients with chronic diskogenic back pain: technical note and preliminary result. J Neurol Surg A Cent Eur Neurosurg. 2017;78(06):529–34. https://doi.org/10.1055/s-­0037-­1604361. Epub 2017 Sep 4 11. Moon BJ, Yi S, Ha Y, Kim KN, Yoon DH, Shin DA.  Clinical efficacy and safety of trans-sacral Epiduroscopic laser decompression compared to percutaneous epidural Neuroplasty. Pain Res Manag. 2019;2019:2893460. 12. Jo D, Lee DJ.  The extent of tissue damage in the epidural space by ho/ YAG laser during epidur-

317 oscopic laser neural decompression. Pain Phys. 2016;19(1):E209–14. 13. Kim SK, Lee SC, Park SW, Kim ES. Complications of lumbar disc herniations following trans-sacral epiduroscopic lumbar decompression: a single center, retrospective study. J Orthop Surg Res. 2017;12(1):187. 14. Ascher PW, Heppner F. CO2-Laser in neurosurgery. Neurosurg Rev. 1984;7:123–13. 15. Joshua Pfefer T, Choi B, Vargas G, McNally KM, Welch AJ. Mechanisms of laser-induced thermal coagulation of whole blood in vitro. Austin, Texas, USA: Biomedical Engineering Program, The University of Texas at Austin; 1999. 16. Buchelt M, Schlangmann B, Schmolke S, Siebert W.  High power ho:YAG laser ablation of intervertebral discs: effects on ablation rates and temperature profile. Lasers Surg Med. 1995;16:179–83. 17. Jeon S, Lee GW, Jeon YD, Park I-H, Hong J, Kim J-D.  A preliminary study on surgical navigation for epiduroscopic laser neural decompression. J Med Eng. 2015;229(10):693–702. 18. Jinyoung O, Jo D. Epiduroscopic laser neural decompression as a treatment for migrated lumbar disc herniation. Medicine (Baltimore). 2018;97(14):e0291. 19. Ding Q, Wei Q, Sheng G, et al. The preventive effect of Decorin on epidural fibrosis and epidural adhesions after laminectomy. Front Pharmacol. 2021;16:774316. 20. Hale GM, Querry MR, Rusk AN, Williams D. Influence of temperature on the spectrum of water. JOSA. 1972;62(9):1103–8. https://doi.org/10.1364/ JOSA.62.001103.

Vertebroplasty and Kyphoplasty Seong Son

1 Introduction The population of the elderly is growing rapidly worldwide; therefore, osteoporosis and the risk of fractures are on the increase [1, 2] and currently affect more than 200 million people worldwide [1]. Approximately 25% of women older than 70 years will experience at least one vertebral body compression fracture, and this increase to more than 50% in women above the age of 80 years [1, 3]. Consequently, it is estimated that approximately 1.4 million cases of new osteoporotic vertebral compression fracture (OVCF) occur in elderly individuals annually worldwide [4, 5]. OVCF is associated with severe pain, poor quality of life, and various complications owing to a vicious cycle. Indeed, the adverse effects of vertebral fractures on most activities of daily living are almost as severe as the effect of hip fractures. Furthermore, physical function, self-esteem, body image, and mood may be adversely affected [6]. Many treatment strategies, including conservative treatment, such as bed rest and medical treatment, percutaneous vertebroplasty (PVP), and percutaneous kyphoplasty (PKP), are available for the management of OVCF.  Since the S. Son (*) Department of Neurosurgery, Gil Medical Center, Gachon University College of Medicine, Incheon, Republic of Korea e-mail: [email protected]

introduction of PVP in the 1980s and the approval of polymethyl methacrylate (PMMA) by the US Food and Drug Administration in 2004, PVP using PMMA has become one of the standard treatments for pain control and early recovery of the ability to perform activities of daily living [7–16]. In South Korea, with the accumulation of clinical evidence of the safety and efficacy of PVP and the advancement of surgical materials based on PMMA, PVP for OVCF has become popular since the 2000s [10, 17]. However, there are many controversies regarding the effectiveness and efficacy of vertebroplasty and kyphoplasty [11, 18, 19] Some studies have questioned their effectiveness and have proposed that the use of vertebral augmentation may not be beneficial when compared to conservative pain management or placebo groups (sham procedure) [19–21]. However, most recent studies have reported that vertebroplasty or kyphoplasty can be used for pain control with significant improvement of pain in 80  ~  90% of patients, improved quality of life, and favorable prognosis, while being cost-effective in patients with OVCF who have appropriate indications compared to the use of conservative treatment [14, 22–31]. Many prospective case series have revealed rapid and lasting pain relief in 80–90% of patients treated with PVP or PKP [29]. In patients with fresh fractures, improvement of pain after vertebroplasty was seen in 93% of cases, while, in older lesions, the treatment was effective in up to

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_29

319

S. Son

320

80% of patients [32]. However, the mechanism of underlying pain relief after vertebroplasty remains unclear. Some studies have suggested that the chemical, thermal, and mechanical effects of PMMA lead to pain relief. Especially, mechanical effects that minimize the micro-­motion of vertebral fractures, which stimulate nociceptors in the endplate and periosteum, have been accepted as the most convincing theory [30, 31, 33]. Generally, once a diagnosis of OVCF is confirmed, the first-line treatment is usually ­conservative pain management with or without some degree of back support and physiotherapy [34, 35]. PVP or balloon-assisted PKP are the two commonly used minimally invasive vertebral augmentation procedures used to restore normal vertebral height, reduce pain, and minimize deformity [34, 36]. PVP, which involves injecting liquid cement (PMMA) via a bone marrow needle under fluoroscopic guidance, is a non-­ complicated surgery that can be performed under local anesthesia. However, liquid cement can leak into extra-vertebral space, blood vessels, or spinal canal during the procedure, and there is a limitation in the efficacy of the procedure in terms of reduction of segmental kyphosis in patients with OVCF.  To overcome these limitations, PKP with balloon expansion was introduced since the late 1990s. Theoretically, after balloon expansion, an efficient volume of cement can be injected at low pressure without the risk of cement leakage. Additionally, balloon expansion increases the height of the collapsed vertebral body and corrects segmental kyphosis. However, although the short-term radiological results can be more favorable than those of vertebroplasty (i.e., more correction of kyphosis and compression ratio), the overall clinical outcomes of both procedures are similar [37–40]. In this chapter, we focused on the detailed surgical techniques of PVP and PKP, as well as their general indications and postoperative care.

2 Indications Algorithms for determining the best treatment option to help guide physicians in treating patients with OVCF have not yet been developed

[41]. Although the American College of Radiology has published some appropriate criteria for different management options, there is still a lack of consensus regarding the development of a standard of care [42]. The only published clinical practice guidelines have been developed by the American Academy of Orthopedic Surgeons (AAOS). Of the 11 recommendations, only one has strong evidence and one has moderate evidence backing them. Consequently, the consensus is ambiguous and relies on the personal judgment of the physician [36]. Unfortunately, as mentioned above, no clear guidelines define the point at which vertebral augmentation should be performed; moreover, some authors have suggested utilizing these approaches prophylactically, even in non-fractured vertebral bodies [43]. Currently, the most common indications for vertebroplasty or kyphoplasty are osteoporotic compression fractures and spinal bone tumors. The surgical technique is the same for both disease entities; however, the detailed indications are different.

2.1 OVCF Most OVCFs respond well to nonoperative treatments. However, approximately one-third of vertebral fractures may become chronically painful [44], and 10% would require hospital admission [45]. The mandatory baseline condition is the diagnosis of acute or recent compression fractures via MRI, CT, or radiography. Although the exact indications for vertebroplasty or kyphoplasty remain obscure, the general indications and goals of surgery are as follows: 1. Ongoing pain despite adequate conservative treatment after the occurrence of a new fracture: The appropriate duration of nonoperative treatment is controversial. Although there are controversies regarding early surgery and later surgery for fractures, early surgery is considered to be more favorable in terms of the degree of pain relief, speed of recovery, and cement distribution in the vertebral body [10, 46]. However, in terms of cost-­

Vertebroplasty and Kyphoplasty

effectiveness, the Health Insurance Review & Assessment service of South Korea recommends that severe pain limiting daily life after a minimum of 2 weeks of nonoperative treatment is a consensus indication. Exceptions to 2  weeks of conservative treatment include those over 80 years of age, and patients with severe comorbidities, such as pneumonia, deep vein thrombosis, congestive heart f­ ailure, uncontrolled diabetes, Kummel’s disease, and bone tumor. On the other hand, in the case of kyphoplasty, the Health Insurance Review & Assessment service of South Korea recommends a minimum of 3 weeks of nonoperative treatment before surgery. 2. Patients with severe pain that patients remain bedridden for more than 4 days. 3. Progressive compression fractures of one or multiple vertebrae with subsequent loss of posture. 4. Nonunion with persistent instability without spontaneous healing (Kummel disease). 5. Elderly patients who are expected to experience complications such as deep vein thrombosis, pneumonia, or sores during bed rest. 6. To reinforce screw fixation in patients with severe osteoporosis.

2.2 Neoplasm Approximately 2000 new cases of bone cancer and 6000 new cases of soft tissue tumors are diagnosed in the United States annually [47]. Of these, only approximately 5% involve the spine. The incidence of primary spinal tumors is estimated at 2.5–8.5 per 100,000 people per year. Tumors of the lymphoid system, such as plasmacytoma, are generally considered in the discussion of spinal tumors. Some bone tumors have a special predilection for the vertebral column (e.g., osteoblastomas), whereas others occur exclusively in the spine (e.g., chordoma). Most spinal tumors in adults are metastatic adenocarcinomas, multiple myelomas, and osteosarcomas [47]. Of the one million new cases of cancer diagnosed annually, two-thirds eventually

321

metastasize [48]. After the lungs and liver, the skeletal system is the third most common site of metastatic diseases, and regardless of the origin of the primary tumor, the spine is the most common site of skeletal metastasis [48]. Autopsy findings indicated that up to 70% of patients with bone metastatic carcinoma have vertebral deposits at the time of death. In about 70% of cases, the metastatic lesion is localized in the thoracic and thoracolumbar regions of the spine, the lumbar and sacral regions are involved in 22% of cases, and the cervical spine in 8% of cases [49]. According to previous studies, the most common primary tumors that metastasize to the spine are tumors of the breast (16.5%), lung (15.6%), prostate (9.2%), and kidney (6.5%) [50]. The primary lesion remains unknown in 12.5% of cases [49]. Most patients with metastatic lesions present between 50 and 60 years of age, and there is no difference in the sex of these patients. These patients are at risk of developing pathological vertebral fractures and symptomatic spinal cord compression with neurological deficits. This danger increases with improvements in oncologic treatment and prolonged life expectancy of these patients. In the1980s, the efficacy and safety of vertebroplasty for spinal bone tumors was proven, especially for metastatic pathological compression fractures [51, 52]. PVP is an adjunctive treatment for severe spinal pain associated with spinal tumors. In addition to the pain relief effect, there are reports that it can slow the progression of the tumor at the injection site of PMMA and cause necrosis of the adjacent tumor tissue in cadaveric examinations [53]. However, the main goal of vertebroplasty or kyphoplasty for metastatic tumors is pain control rather than tumor control [54]. Tumors that can be treated with PVP are as follows: 1. Hemangioma. 2. Hematological malignancies (myeloma or lymphoma). 3. Metastatic tumor: kidney, breast, lung, liver, bladder, thyroid, or prostate caner 4. Pheochromocytoma

322

3 Contraindications 1. Pain unlikely to be related to a fracture. 2. Infection. 3. Blood clotting disorders. 4. Neurological compromise including paralysis or urinary/defecation abnormality: impingement of the spinal cord or nerve root, epidural extension of metastatic tumor, and compromising the spinal canal (if an open procedure appears more appropriate). 5. Impaired pedicle visibility intraoperatively. 6. Poor general status of the patient, inability to stand in the prone position. 7. Vertebra plana (relative). 8. Hypersensitivity to PMMA components or contrast allergies. 9. Pregnant or lactating women and women with childbearing potential who plan to become pregnant. 10. Solid tissues or osteoblastic tumors.

4 Step-by-Step Technique Key preparations for vertebroplasty/kyphoplasty include high-quality fluoroscopy (C-arm), cement application using small syringes (1  cc), guidewire, large-diameter cannulas (8G), and cement with radiopacity and high/adapted viscosity. The key steps of vertebroplasty/kyphoplasty are listed below: 1. Positioning and monitoring patient, as well as securing intravenous access. 2. Image control prior to draping and marking of levels to be treated. 3. Local anesthesia in line with the pedicles with or without sedation (unless general anesthesia is used). 4. Stab incision.

S. Son

5. Adjustment of bone marrow needle with or without guidewire insertion and placement of filling cannulas. 6. In case of kyphoplasty, insertion of ballooning instrument and expansion of the balloon. 7. Preparation of cement according to recommendations of the manufacturer, and distribution into small syringes. 8. Cement application with adequate viscosity; high viscous cement is inserted with the aid of 1 cc syringes or a trocar. 9. Bone marrow needle or cannula removal and suturing after curing of the cement. 10. In some cases, a unilateral or extra-pedicular approach can be used.

1. Place the patient in the prone position, monitor, and secure intravenous access. All vertebroplasty procedures are performed with the patient in the prone position while lying on a radiolucent bed with a C-arm. An aseptic drape is used to cover the surgical level widely in the basic step (Fig. 1). 2. Confirm the surgical level via a true image in the anteroposterior (A-P) and lateral views using fluoroscopy. Drawing the pedicles and margins of the vertebral body (Fig. 2). 3. Local anesthesia in line with the pedicles with or without sedation (unless general anesthesia is used). After the patient is placed in the prone position on a radiolucent bed, local anesthesia and slight sedation using midazolam or diazepam are administered. 4. Stab incision at the insertion point. A stab incision is made using a #11 blade, approximately apart 0.5–1  cm from the lateral margin of the pedicle based on preoperative MRI or CT images or patient obesity (Fig. 3).

Vertebroplasty and Kyphoplasty

323

Fig 1  A patient in the prone position on the spine bed and setting of the C-arm

Fig. 2  Drawing the vertebral body and pedicle using guidewire marker

5. Insertion of bone marrow needle (Jamshidi needle) under fluoroscopic guidance. A 10-G vertebroplasty needle is inserted into the vertebral body through the bilateral transpedicular approach. Although the entry point may vary depending on the target area of vertebroplasty, the entry point is generally 9–11 o’clock in the left pedicle and 1–3 o’clock in the right pedicle (Fig. 4). When the end of the needle approaches the medial margin of the pedicle in the A-P view, we should check the lateral view to

ensure that the central canal is not invaded. If the end of the needle is medial to the circle of the pedicle in the A-P view and posterior to the dorsal margin of the vertebral body in the lateral view, it is suspected that the needle has invaded the central canal. The insertion trajectory should be modified according to the various situations of fluoroscopy in the A-P and lateral views (Fig. 5). Moreover, needle advancement may vary depending on the target area of vertebroplasty. However, the advancement of the

S. Son

324

Fig. 3  Stab incision using a #11 blade

needle is usually better performed diagonally from the posterior superior corner to the anterior inferior corner of the vertebral body to cover as much area of the vertebral body as possible (Fig. 6). In general, the bilateral transpedicular approach is preferred for sufficient cement distribution (Fig. 7). Some surgeons prefer to insert a guidewire and place a working channel and a filling cannula (bone void filler) for low pressure and sufficient volume during cement injection. In the case of kyphoplasty, insertion of guidewire(s) and placement of thick cannulas (working channels) is mandatory (Fig. 8). 6. In case of kyphoplasty, insertion of ballooning instrument and expansion of the balloon.

Fig. 4  Insertion point of the needle and target of trajectory in the lateral view

Fig. 5  Correctly inserted needle via the pedicle without invading the central canal

Vertebroplasty and Kyphoplasty

325

Bone entry point Needle trajectory 1/2 height

Ant 1/3

Fig. 6  Advancement of the needle diagonally into the anterior portion of the vertebral body

Fig. 7  Final location of the needle via the bilateral transpedicular approach

A balloon inflation set can be used during kyphoplasty. After insertion of the working channel and removal of the guidewire, an empty space is created in the vertebral body by twisting the insertion of a hand drill, 2 mm posterior to the ventral margin of the vertebral body. The bone void filler is then inserted and moved into the vertebral body to confirm the empty space in the vertebral body. Subsequently, the balloon is inserted into the target space, and the balloon is inflated using fluid-containing contrast to expand the vertebral body’s height under C-arm guidance. The same procedure could be performed simultaneously on the contralateral side. Fig. 8  Filling cannula or bone void filler

S. Son

326

When the pressure of the balloon is too high, the balloon may burst, so care should be taken not to exceed 250 pounds per square inch. In addition, when the volume of the balloon is too large, the endplate of the vertebral body may be disrupted; therefore, attention should be paid to fluoroscopy while ballooning. Generally, a maximum of 3  ~  4.5  cc of expansion volume is recommended (Figs. 9 and 10). 7. Preparation of cement according to recommendations of the manufacturer, and cement distribution into small syringes or a bone void filler. Usually, the viscosity for each procedure is set up as highly viscous, similar to that of toothpaste, approximately 5 min after mixing. PVP with high viscosity not only reduces the risk of cement leakage, especially in the paravertebral area and periph-

eral vein, but also has satisfactory clinical effects [55]. 8. Cement application with adequate viscosity, and high viscous cement is inserted with the aid of 1 cc syringes or a bone void filler. PMMA is slowly injected using a 1-cc syringe or bone void filler until satisfactory filling and distribution in the vertebral body is achieved [56]. The volume of the inserted PMMA is determined according to the literature and discretion of the surgeon [57–59] (Fig. 11). Surgeons need not feel compelled to inject a particular cement volume in the pursuit of better clinical outcomes but should strive to achieve safe filling of individual vertebral bodies [58]. However, there are some controversies regarding the optimal injection volume of cement. Although a greater volume of bone cement injected during vertebroplasty contributes to the risk of extra-vertebral leakage or subsequent adjacent fracture, it results in a greater improvement in kyphosis [60]. Furthermore, compressive stiffness and intradiscal pressure also increase with increasing the percentage of cement fill. According to previous literature, on average, restoration of strength and stiffness requires vertebral body cement fills of 16.2% and 29.8%, respectively [57]. Approximately 15% of cement fill is the limit beyond which no substantial increase in compressive stiff-

Fig. 9  Balloon inflation set

Fig. 10  Diagonal balloon insertion, similar to vertebroplasty, and adequate inflation of bilateral balloons

Vertebroplasty and Kyphoplasty

Fig. 11  Serial fluoroscopic picture during cement injection

327

328

ness or intradiscal pressure could be detected and is the minimum volume of cement we recommend for vertebroplasty. In other words, in the average thoracolumbar vertebra, this finding indicates that 4–6  mL of cement injection is appropriate [59]. Regarding the location of cement distribution, vertebral heights did not significantly differ between the augmented and final compression states in any location, central or lateral side. In addition, the height loss between the central and lateral locations of the injections did not differ significantly [61]. The use of a bone void filler for PVP may increase the injected volume of cement and easily control the depth and direction of PMMA, which may reduce cement leakage. However, pain improvement did not differ between the bone void filler and Jamshidi needle groups [62]. The usage of a bone void filler for PVP may be an alternative to the Jamshidi needle in selected cases. During the injection of cement, fluoroscopy should be frequently performed to check for leakage from the vertebral body. If any leakage is identified, the needle must be repositioned, the cement should be allowed to harden, or in extreme cases, suspend the procedure. 9. Bone marrow needle or cannula removal and suture. After confirming that the PMMA has hardened adequately, the needle or cannula should be removed from the vertebral body. If the needle is withdrawn before the cement has hardened sufficiently, it may leak along the needle trajectory of the pedicle. Finally, a one-point skin suture using nylon 3–0 or a skin tape is performed on each side.

S. Son

10. Unilateral or extra-pedicular approach. In cases of a difficult transpedicular approach, such as mid or upper thoracic level, an extremely small pedicle diameter, or an invisible pedicle on fluoroscopy, the unilateral extra-pedicular approach can be useful. The insertion point of the Jamshidi needle is far from the lateral margin of the pedicle in the A-P view, and the insertion angle is gentler than that of the transpedicular approach. In the case of mid or upper thoracic level, the insertion point of the needle in the costotransverse joint and the insertion angle is gentle, usually 45°. The target direction is the contralateral inferior corner of the vertebral body on the A-P view and the inferoanterior corner of the vertebral body on the lateral view. When the end of the needle is ventral to the posterior margin of the vertebral body in the lateral view, it should be kept outside the border of the lateral margin of the pedicle in the A-P view. Usually, the tip of the needle is in the center of the vertebral body in the A-P and lateral views. The process is the same as that of the transpedicular approach (Fig. 12). Both bilateral and unilateral cement augmentation are relatively safe and effective treatments for patients with painful OVCF.  Compared to bilateral procedures, unilateral procedures may achieve similar clinical results in the treatment of OVCFs when assessed in terms of pain relief, improvements in quality of life, and surgery-­ related complications [63]. However, unilateral procedures have a shorter operation time, less radiation dose, less volume of injected cement, less leakage of cement, and less surgery-related costs than bilateral procedures [64–67].

Vertebroplasty and Kyphoplasty

329

a

b

d

c

e

Fig. 12 (a) Insertion of needle targeting costovertebral junction; (b) Advancement of needle to center of the vertebral body through costovetebral junction; (c) Insertion of balloon; (d) Inflation of balloon; (e) Injection of cement

5 Postoperative Consideration and Case Illustration 5.1 Complications 1. New compression fracture in adjacent vertebral body or refracture: The risk of fracture at the adjacent levels seems to increase after cement reinforcement [68–72]. However, the natural history of OVCF needs to be considered, as the risk of a new fracture increases exponentially with an increasing number of fractures. Consequently, some studies have argued that cement augmentation has no effect on the recurrence rate [73–75]. A larger systematic study or big data study is required to confirm this conclusion. 2. Extra-vertebral cement leakage:

The incidence of cement leakage in PVP and PKP was reported to be 54.7% and 18.4% (14–72%) [76]. The results of this meta-analysis suggest patients with ­intravertebral cleft, cortical disruption, low cement viscosity, and high volume of injected cement may be at a high risk of cement leakage after vertebroplasty or kyphoplasty [77] (Fig. 13). 3. Transient fever. 4. Transient exacerbation of pain. 5. Rib and sternal fractures. 6. Pedicle fracture. 7. Transverse process fracture. 8. Neurological complication: spinal canal encroachment, spinal cord injury, nerve root compression (Fig. 14). 9. Infection.

330

S. Son

Fig. 13  Case illustration. A 73-year-­old female patient with a surgical site infection 3 months after vertebroplasty of the L4 and L5

Vertebroplasty and Kyphoplasty

331

Fig. 14  Case illustration. A 75-year-­old female patient with cement leakage into the central spinal canal after vertebroplasty of the L2

10. Cement embolism: pulmonary, renal, car diac, and cerebral. 11. Fat embolism. 12. Cement toxicity.

6 Summary Vertebroplasty and kyphoplasty are simple, minimally invasive surgeries for effective pain control and rapid recovery of the ability to perform daily life activities in patients with osteoporotic compression fractures or vertebral body tumors, such as metastasis or hematologic malignancy. Surgeons should be familiar with the appropriate indications, accurate detailed surgical techniques and knowledge, and possible complications. These procedures make it possible to cope with the increasing population of the elderly and the prevalence of compression fractures.

References 1. Kanis JA.  Diagnosis of osteoporosis and assessment of fracture risk. Lancet (London, England). 2002;359(9321):1929–36. 2. Lane NE.  Epidemiology, etiology, and diagnosis of osteoporosis. Am J Obstet Gynecol. 2006;194(Suppl. 2):S3–11. 3. Lee YL, Yip KM. The osteoporotic spine. Clin Orthop Relat Res. 1996;323:91–7. 4. Borgström F, Zethraeus N, Johnell O, et  al. Costs and quality of life associated with osteoporosis-­ related fractures in Sweden. Osteoporos Int. 2006;17(5):637–50. 5. Johnell O, Kanis JA.  An estimate of the worldwide prevalence and disability associated with osteoporotic fractures. Osteoporos Int. 2006;17(12):1726–33. 6. Lippuner K, Golder M, Greiner R.  Epidemiology and direct medical costs of osteoporotic fractures in men and women in Switzerland. Osteoporos Int. 2005;16(Suppl 2):S8–s17. 7. Gangi A, Kastler BA, Dietemann JL.  Percutaneous vertebroplasty guided by a combination of CT and fluoroscopy. AJNR Am J Neuroradiol. 1994;15(1):83–6.

332 8. Deramond H, Depriester C, Toussaint P.  Vertebroplasty and percutaneous interventional radiology in bone metastases: techniques, indications, contra-­ indications. Bull Cancer Radiother. 1996;83(4):277–82. 9. Jensen ME, Evans AJ, Mathis JM, Kallmes DF, Cloft HJ, Dion JE.  Percutaneous polymethylmethacrylate vertebroplasty in the treatment of osteoporotic vertebral body compression fractures: technical aspects. AJNR Am J Neuroradiol. 1997;18(10):1897–904. 10. Son S, Lee SG, Kim WK, Park CW, Yoo CJ.  Early Vertebroplasty versus delayed Vertebroplasty for acute osteoporotic compression fracture: are the results of the two surgical strategies the same? J Korean Neurosurg Soc. 2014;56(3):211–7. 11. Guo JB, Zhu Y, Chen BL, al. Surgical versus non-­ surgical treatment for vertebral compression fracture with osteopenia: a systematic review and meta-­analysis. PLoS One. 2015;10(5):e0127145. 12. Lou S, Shi X, Zhang X, Lyu H, Li Z, Wang Y.  Percutaneous vertebroplasty versus non-operative treatment for osteoporotic vertebral compression fractures: a meta-analysis of randomized controlled trials. Osteoporos Int. 2019;30(12):2369–80. 13. Balkarli H, Kilic M, Balkarli A, Erdogan M.  An evaluation of the functional and radiological results of percutaneous vertebroplasty versus conservative treatment for acute symptomatic osteoporotic spinal fractures. Injury. 2016;47(4):865–71. 14. Yang EZ, Xu JG, Huang GZ, et  al. Percutaneous Vertebroplasty versus conservative treatment in aged patients with acute osteoporotic vertebral compression fractures: a prospective randomized controlled clinical study. Spine. 2016;41(8):653–60. 15. Voormolen MH, Mali WP, Lohle PN, et  al. Percutaneous vertebroplasty compared with optimal pain medication treatment: short-term clinical outcome of patients with subacute or chronic painful osteoporotic vertebral compression fractures. The VERTOS study. AJNR Am J Neuroradiol. 2007;28(3):555–60. 16. Buchbinder R, Osborne RH, Ebeling PR, et  al. Efficacy and safety of vertebroplasty for treatment of painful osteoporotic vertebral fractures: a randomised controlled trial [ACTRN012605000079640]. BMC Musculoskelet Disord. 2008;9:156. 17. Park HB, Son S, Jung, JM, Lee, SG, Yoo BR. Safety and Efficacy of Bone Cement (Spinofill®) for Vertebroplasty in Patients with Osteoporotic Compression Fracture: A Preliminary Prospective Study. J Korean Neurosrug Soc. 2022;65(5): 730–40. 18. Buchbinder R, Johnston RV, Rischin KJ, et  al. Percutaneous vertebroplasty for osteoporotic vertebral compression fracture. Cochrane Database Syst Rev. 2018;4(4):Cd006349. 19. Stevenson M, Gomersall T, Lloyd Jones M, et  al. Percutaneous vertebroplasty and percutaneous balloon kyphoplasty for the treatment of osteoporotic vertebral fractures: a systematic review and

S. Son cost-effectiveness analysis. Health Technol Assess (Winchester, England). 2014;18(17):1–290. 20. Buchbinder R, Osborne RH, Ebeling PR, et  al. A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures. N Engl J Med. 2009;361(6):557–68. 21. Kallmes DF, Comstock BA, Heagerty PJ, et  al. A randomized trial of vertebroplasty for osteoporotic spinal fractures. N Engl J Med. 2009;361(6):569–79. 22. Klazen CA, Lohle PN, de Vries J, et al. Vertebroplasty versus conservative treatment in acute osteoporotic vertebral compression fractures (Vertos II): an open-­ label randomised trial. Lancet (London, England). 2010;376(9746):1085–92. 23. Lin JH, Chien LN, Tsai WL, Chen LY, Chiang YH, Hsieh YC.  Early vertebroplasty associated with a lower risk of mortality and respiratory failure in aged patients with painful vertebral compression fractures: a population-based cohort study in Taiwan. Spine J. 2017;17(9):1310–8. 24. Láinez Ramos-Bossini AJ, López Zúñiga D, Ruiz SF.  Percutaneous vertebroplasty versus conservative treatment and placebo in osteoporotic vertebral fractures: meta-analysis and critical review of the literature. Eur Radiol. 2021;31(11):8542–53. 25. Sanli I, van Kuijk SMJ, de Bie RA, van Rhijn LW, Willems PC.  Percutaneous cement augmentation in the treatment of osteoporotic vertebral fractures (OVFs) in the elderly: a systematic review. Eur Spine J. 2020;29(7):1553–72. 26. Yuan WH, Hsu HC, Lai KL. Vertebroplasty and balloon kyphoplasty versus conservative treatment for osteoporotic vertebral compression fractures: a meta-­ analysis. Medicine. 2016;95(31):e4491. 27. Mattie R, Laimi K, Yu S, Saltychev M.  Comparing percutaneous Vertebroplasty and conservative therapy for treating osteoporotic compression fractures in the thoracic and lumbar spine: a systematic review and meta-analysis. J Bone Joint Surg Am. 2016;98(12):1041–51. 28. Pron G, Hwang M, Smith R, Cheung A, Murphy K. Cost-effectiveness studies of vertebral augmentation for osteoporotic vertebral fractures: a systematic review. Spine J. 2022;25(8):923–8. 29. Barr JD, Barr MS, Lemley TJ, McCann RM.  Percutaneous vertebroplasty for pain relief and spinal stabilization. Spine (Phila Pa 1976). 2000;25(8):923–8. 30. Heini PF, Wälchli B, Berlemann U.  Percutaneous transpedicular vertebroplasty with PMMA: operative technique and early results. A prospective study for the treatment of osteoporotic compression fractures. Eur Spine J. 2000;9(5):445–50. 31. Pérez-Higueras A, Alvarez L, Rossi RE, Quiñones D, Al-Assir I.  Percutaneous vertebroplasty: long-term clinical and radiological outcome. Neuroradiology. 2002;44(11):950–4. 32. Brown DB, Gilula LA, Sehgal M, Shimony JS. Treatment of chronic symptomatic vertebral com-

Vertebroplasty and Kyphoplasty pression fractures with percutaneous vertebroplasty. AJR Am J Roentgenol. 2004;182(2):319–22. 33. Kaufmann TJ, Jensen ME, Schweickert PA, Marx WF, Kallmes DF.  Age of fracture and clinical outcomes of percutaneous vertebroplasty. AJNR Am J Neuroradiol. 2001;22(10):1860–3. 34. Ensrud KE, Schousboe JT. Clinical practice. Vertebral fractures. N Engl J Med. 2011;364(17):1634–42. 35. Stadhouder A, Buskens E, Vergroesen DA, Fidler MW, de Nies F, Oner FC.  Nonoperative treatment of thoracic and lumbar spine fractures: a prospective randomized study of different treatment options. J Orthop Trauma. 2009;23(8):588–94. 36. McConnell CT Jr, Wippold FJ 2nd, Ray CE Jr, et al. ACR appropriateness criteria management of vertebral compression fractures. J Am Coll Radiol. 2014;11(8):757–63. 37. Rodriguez AJ, Fink HA, Mirigian L, et  al. Pain, quality of life, and safety outcomes of Kyphoplasty for vertebral compression fractures: report of a task force of the American Society for Bone and Mineral Research. J Bone Miner Res Off J Am Soc Bone Miner Res. 2017;32(9):1935–44. 38. Wang H, Sribastav SS, Ye F, et al. Comparison of percutaneous Vertebroplasty and balloon Kyphoplasty for the treatment of single level vertebral ­compression fractures: a meta-analysis of the literature. Pain Physician. 2015;18(3):209–22. 39. Gu CN, Brinjikji W, Evans AJ, Murad MH, Kallmes DF.  Outcomes of vertebroplasty compared with kyphoplasty: a systematic review and meta-analysis. J Neurointerv Surg. 2016;8(6):636–42. 40. Huang X, Chang H, Xu H, Chen X, Wang H, Song Y.  Comparison of outcomes between percutaneous vertebroplasty and percutaneous kyphoplasty for the treatment of Kümmell’s disease: a meta-analysis. Clinical Spine Surg. 2021;35(6):276–86. 41. Genev IK, Tobin MK, Zaidi SP, Khan SR, Amirouche FML, Mehta AI.  Spinal compression fracture management: a review of current treatment strategies and possible future avenues. Global spine J. 2017;7(1):71–82. 42. Esses SI, McGuire R, Jenkins J, et al. The treatment of symptomatic osteoporotic spinal compression fractures. J Am Acad Orthop Surg. 2011;19(3):176–82. 43. Kobayashi N, Numaguchi Y, Fuwa S, et  al. Prophylactic vertebroplasty: cement injection into non-fractured vertebral bodies during percutaneous vertebroplasty. Acad Radiol. 2009;16(2):136–43. 44. Cooper C, Atkinson EJ, O'Fallon WM, Melton LJ 3rd. Incidence of clinically diagnosed vertebral fractures: a population-based study in Rochester, Minnesota, 1985-1989. J Bone Miner Res Off J Am Soc Bone Miner Res. 1992;7(2):221–7. 45. Silverman SL.  The clinical consequences of vertebral compression fracture. Bone. 1992;13(Suppl 2):S27–31. 46. Diamond T, Clark W, Bird P, Gonski P, Barnes E, Gebski V. Early vertebroplasty within 3 weeks of fracture for acute painful vertebral osteoporotic fractures:

333 subgroup analysis of the VAPOUR trial and review of the literature. Eur Spine J. 2020;29(7):1606–13. 47. Jemal A, Murray T, Ward E, et  al. Cancer statistics, 2005. CA Cancer J Clin. 2005;55(1):10–30. 48. Boland PJ, Lane JM, Sundaresan N. Metastatic disease of the spine. Clin Orthop Relat Res. 1982;169:95–102. 49. Brihaye J, Ectors P, Lemort M, Van Houtte P.  The management of spinal epidural metastases. Adv Tech Stand Neurosurg. 1988;16:121–76. 50. Nottebaert M, von Hochstetter AR, Exner GU, Schreiber A.  Metastatic carcinoma of the spine. A study of 92 cases. Int Orthop. 1987;11(4):345–8. 51. Jang JS, Lee SH.  Efficacy of percutaneous vertebroplasty combined with radiotherapy in osteolytic metastatic spinal tumors. J Neurosurg Spine. 2005;2(3):243–8. 52. Health Quality Ontario. Vertebral augmentation involving vertebroplasty or kyphoplasty for cancer-­ related vertebral compression fractures: a systematic review. Ont Health Technol Assess Ser. 2016;16(11):1–202. 53. Cardoso ER, Ashamalla H, Weng L, et  al. Percutaneous tumor curettage and interstitial delivery of samarium-153 coupled with kyphoplasty for treatment of vertebral metastases. J Neurosurg Spine. 2009;10(4):336–42. 54. Pilitsis JG, Rengachary SS.  The role of vertebroplasty in metastatic spinal disease. Neurosurg Focus. 2001;11(6):e9. 55. Zhang ZF, Yang JL, Jiang HC, et al. An updated comparison of high- and low-viscosity cement vertebroplasty in the treatment of osteoporotic thoracolumbar vertebral compression fractures: a retrospective cohort study. Int J Surg (London, England). 2017;43: 126–30. 56. Wang H, Zhang T, Cheung KM, Shea GK. Application of deep learning upon spinal radiographs to predict progression in adolescent idiopathic scoliosis at first clinic visit. EClinical Medicine. 2021;42:101220. 57. Molloy S, Mathis JM, Belkoff SM.  The effect of vertebral body percentage fill on mechanical behavior during percutaneous vertebroplasty. Spine. 2003;28(14):1549–54. 58. Kaufmann TJ, Trout AT, Kallmes DF.  The effects of cement volume on clinical outcomes of percutaneous vertebroplasty. AJNR Am J Neuroradiol. 2006;27(9):1933–7. 59. Martinčič D, Brojan M, Kosel F, et  al. Minimum cement volume for vertebroplasty. Int Orthop. 2015;39(4):727–33. 60. Li YA, Lin CL, Chang MC, Liu CL, Chen TH, Lai SC.  Subsequent vertebral fracture after vertebroplasty: incidence and analysis of risk factors. Spine. 2012;37(3):179–83. 61. Molloy S, Riley LH 3rd, Belkoff SM. Effect of cement volume and placement on mechanical-property restoration resulting from vertebroplasty. AJNR Am J Neuroradiol. 2005;26(2):401–4. 62. Jeon SI, Choe IS, Kwon YS, Seo DH, Lee KC, Park SC.  Comparative clinical results of vertebroplasty

334 using jamshidi® needle and bone void filler for acute vertebral compression fractures. Korean J Spine. 2012;9(3):239–43. 63. Yan L, He B, Guo H, Liu T, Hao D.  The prospective self-controlled study of unilateral transverse process-pedicle and bilateral puncture techniques in percutaneous kyphoplasty. Osteoporos Int. 2016;27(5):1849–55. 64. Chang W, Zhang X, Jiao N, et  al. Unilateral versus bilateral percutaneous kyphoplasty for osteoporotic vertebral compression fractures: a meta-analysis. Medicine. 2017;96(17):e6738. 65. Yin P, Ji Q, Wang Y, et al. Percutaneous kyphoplasty for osteoporotic vertebral compression fractures via unilateral versus bilateral approach: a meta-analysis. J Clin Neurosci. 2019;59:146–54. 66. Zhiyong C, Yun T, Hui F, Zhongwei Y, Zhaorui L. Unilateral versus bilateral balloon kyphoplasty for osteoporotic vertebral compression fractures: a systematic review of overlapping meta-analyses. Pain Physician. 2019;22(1):15–28. 67. Chen Y, Zhang H, Chen H, Ou Z, Fu Y, Zhang J.  Comparison of the effectiveness and safety of unilateral and bilateral percutaneous vertebroplasty for osteoporotic vertebral compression fractures: a protocol for systematic review and meta-analysis. Medicine. 2021;100(51):e28453. 68. Blasco J, Martinez-Ferrer A, Macho J, San Roman L, Pomés J, Carrasco J, et al. Effect of vertebroplasty on pain relief, quality of life, and the incidence of new vertebral fractures: a 12-month randomized follow­up, controlled trial. J Bone Miner Res Off J Am Soc Bone Miner Res. 2012;27(5):1159–66. 69. Ahn Y, Lee JH, Lee HY, Lee SH, Keem SH. Predictive factors for subsequent vertebral fracture after percutaneous vertebroplasty. J Neurosurg Spine. 2008;9(2):129–36.

S. Son 70. Luo J, Annesley-Williams DJ, Adams MA, Dolan P.  How are adjacent spinal levels affected by vertebral fracture and by vertebroplasty? A biomechanical study on cadaveric spines. Spine J. 2017;17(6): 863–74. 71. Ma X, Xing D, Ma J, et al. Risk factors for new vertebral compression fractures after percutaneous vertebroplasty: qualitative evidence synthesized from a systematic review. Spine. 2013;38(12):E713–22. 72. Xie W, Jin D, Wan C, et  al. The incidence of new vertebral fractures following vertebral augmentation: a meta-analysis of randomized controlled trials. Medicine. 2015;94(37):e1532. 73. Klazen CA, Venmans A, de Vries J, et al. Percutaneous vertebroplasty is not a risk factor for new osteoporotic compression fractures: results from VERTOS II. AJNR Am J Neuroradiol. 2010;31(8):1447–50. 74. Li HM, Zhang RJ, Gao H, Jia CY, et al. New vertebral fractures after osteoporotic vertebral compression fracture between balloon kyphoplasty and nonsurgical treatment PRISMA. Medicine. 2018;97(40):e12666. 75. Zhang H, Xu C, Zhang T, Gao Z, Zhang T. Does percutaneous vertebroplasty or balloon kyphoplasty for osteoporotic vertebral compression fractures increase the incidence of new vertebral fractures? A Meta-­ Analysis. Pain Physician. 2017;20(1):E13–e28. 76. Ryu KS, Park CK, Kim MC, Kang JK.  Dose-­ dependent epidural leakage of polymethylmethacrylate after percutaneous vertebroplasty in patients with osteoporotic vertebral compression fractures. J Neurosurg. 2002;96(1 Suppl):56–61. 77. Zhan Y, Jiang J, Liao H, Tan H, Yang K.  Risk factors for cement leakage after vertebroplasty or kyphoplasty: a meta-analysis of published evidence. World Neurosurg. 2017;101:633–42.

Part IV Motion Preservation Techniques

History and Bascic Concepts of Motion Preservation Tehniques Seung Myung Lee

1 Introduction Spinal intersegmental fusion and screw fixation are common surgical techniques for the treatment of degenerative spinal diseases. It has been used by surgeons for a long time as a technique to promote spinal stabilization after surgical resection of a wide range of spinal structures for neural decompression. In cases of cervical spondylosis or disc herniation, anterior cervical discectomy and fusion (ACDF) is the most common and well-established surgical treatment. Since it was first reported by Robinson and Smith in 1950 and later by Cloward et al., many excellent therapeutic results have been reported for the treatment of cervical degenerative diseases. One of them is thoracolumbar fusion, which has significantly improved over the past few decades. However, the fundamental disadvantage of the fusion technique is that it replaces a functionally mobile and stable segment in a fixed state. In the analysis of physical stress between cervical segments, intersegmental fixation increased longitudinal strain, resulting in increased tension in the adjacent segments. This is thought to accelerate degenerative changes in adjacent segments. Osteophyte formation and destabilizing changes in adjacent segments after fusion have been S. M. Lee (*) Chosun University Hospital, Gwangju, Republic of Korea e-mail: [email protected]

observed radiologically. However, these changes are not always consistent with the clinical presentation. In addition, the side effects related to bone grafts cannot be ignored. To overcome these shortcomings of fusion surgery, various dynamic stabilization concepts with motion preservation and related devices have been developed.

2 Main Text Cervical artificial disk replacement (CADR) has recently been proposed as an alternative to fusion surgery. Theoretically, CADR has the advantages of maintaining the mobility of the cervical segment, preventing degenerative changes in adjacent segments, and maintaining the height and stability of the nucleus pulposus [1–3]. In addition, it reduces the side effects caused by limiting cervical spine movement until intervertebral fusion occurs after the fusion surgery, allowing to quickly return to the previous normal function [4–7]. However, more negative results of CADR than anticipated have been reported since the release of 5-year follow-up reports. It is believed that this negative opinion narrowed the surgical indication, and significantly reduced the frequency of surgery for CADR compared to the initial stage. Representative examples include postoperative cervical kyphosis due to heterotopic ossification, delayed osseointegration at the periphery of the intervertebral disc, asymmetric

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_30

337

S. M. Lee

338

endplate treatment, and exacerbation of axial pain due to deterioration of spinal stability and economic feasibility [8, 9]. On the other hand, there are many statistically significant optimistic results such as the rate of corrective surgery for fusion and maintenance of kinematic factors when observed for more than 5 years [10–14]. In the surgical treatment of lumbar degenerative disc disease, lumbar artificial disc replacement (LADR) has been developed to compensate for the shortcomings of classical osteosyntheses, such as pseudoarthrosis, graft-related complications, and adjacent segment syndrome [15–19]. It was developed to preserve the spine and to maintain normal spinal mechanics. Initial clinical results indicated satisfactory therapeutic effects. However, there is no clear difference in the incidence of adjacent segment syndrome in long-­ term follow-up results, and there are many reports that the initial therapeutic effect gradually decreased with time [20, 21]. Therefore, the frequency of use and interest gradually decreased in the field. The interspinous process device (IPD) is an instrument used for inserting and fixing spinous processes located in the posterior column of the spine [22]. First, it was developed and commercialized as a method of dynamic stabilization to avoid sagittal extension and intra-discal pressure, restore foraminal height, and provide spinal stability without intersegmental immobilization [23–26]. According to the literature records of the spinous process apparatus in the 1950s, Dr. Knowles inserted a metal structure between the spinous processes. Several similar products have been produced for several decades. While many clinical journals on biomechanical experiments have been published, the long-term results remain controversial [27, 28]. Lastly, there is dynamic posterior stabilization using a screw and dynamic rod system. This method uses the existing principles of controlling the neutral position of the spinal segment, controlling flexion and extension in the sagittal plane, reducing the load on the intervertebral disc, modifying motion, and modifying the load distribution within the segment [29–31]. This has

great significance in preventing problems that occur during fusion and preserving motion [32, 33]. To date, various types of products have been developed and tried in combination with a pedicle screw, but they cannot replace fusion surgery yet and are only used as an auxiliary means of the fusion technique. The concept and principle of dynamic posterior stabilization have taken root to some extent, as there is no long-term follow-up study that satisfies the concept and principle.

3 Summary • CADR is a good alternative to ACDF. • LADR has been evaluated to be unsatisfactory in its effectiveness and is gradually decreasing in frequency. • Although IPD and screw-dynamic rod systems are being tested in various ways, they cannot completely replace fusion surgery, since more long-term follow-up data are needed.

References 1. Nunley P, Schouwen KFV, Stone M.  Cervical Total disc replacement: indications and technique. Neurosurg Clin N Am. 2021;32(4):419–24. 2. Xu S, et al. Adjacent segment degeneration or disease after cervical total disc replacement: a meta-analysis of randomized controlled trials. J Orthop Surg Res. 2018;13(1):244. 3. Zhai S, et  al. Total disc replacement compared with fusion for cervical degenerative disc disease: a systematic review of overlapping meta-analyses. Medicine (Baltimore). 2020;99(19):e20143. 4. Alves OL.  Cervical Total disc replacement: expanded indications. Neurosurg Clin N Am. 2021;32(4):437–48. 5. Callanan G, Radcliff KE. Cervical Total disc replacement: long-term outcomes. Neurosurg Clin N Am. 2021;32(4):461–72. 6. Delamarter RB, Zigler J. Five-year reoperation rates, cervical total disc replacement versus fusion, results of a prospective randomized clinical trial. Spine (Phila Pa 1976). 2013;38(9):711–7. 7. Takayasu M.  Cervical total disc replacement:history and future perspectives. No Shinkei Geka. 2020;48(7):579–86.

History and Bascic Concepts of Motion Preservation Tehniques 8. Parish JM, Asher AM, Coric D.  Complications and complication avoidance with cervical Total disc replacement. Int J Spine Surg. 2020;14(s2):S50–6. 9. Price RL, Coric D, Ray WZ.  Cervical total disc replacement: complications and complication avoidance. Neurosurg Clin N Am. 2021;32(4):473–81. 10. Findlay C, Ayis S, Demetriades AK. Total disc replacement versus anterior cervical discectomy and fusion: a systematic review with meta-analysis of data from a total of 3160 patients across 14 randomized controlled trials with both short- and medium- to long-term outcomes. Bone Joint J. 2018;100-B(8):991–1001. 11. Heller JG, et  al. Comparison of BRYAN cervical disc arthroplasty with anterior cervical decompression and fusion: clinical and radiographic results of a ­randomized, controlled, clinical trial. Spine (Phila Pa 1976). 2009;34(2):101–7. 12. Janssen ME, et  al. ProDisc-C Total disc replacement versus anterior cervical discectomy and fusion for single-level symptomatic cervical disc disease: seven-year follow-up of the prospective randomized U.S.  Food and Drug Administration investigational device exemption study. J Bone Joint Surg Am. 2015;97(21):1738–47. 13. Lobo J, et  al. Results of total cervical disc replacement with a minimum follow-up of 10 years. Rev Bras Ortop (Sao Paulo). 2020;55(2):185–90. 14. Ryu WH, Kowalczyk I, Duggal N.  Long-term kinematic analysis of cervical spine after single-level implantation of Bryan cervical disc prosthesis. Spine J. 2013;13(6):628–34. 15. Auerbach JD, et  al. Evaluation of spinal kinematics following lumbar total disc replacement and circumferential fusion using in vivo fluoroscopy. Spine (Phila Pa 1976). 2007;32(5):527–36. 16. Fras CI, Auerbach JD.  Prevalence of lumbar total disc replacement candidates in a community-based spinal surgery practice. J Spinal Disord Tech. 2008;21(2):126–9. 17. Le Huec JC, et  al. Clinical results of maverick lumbar total disc replacement: two-year prospective follow-­up. Orthop Clin North Am. 2005;36(3): 315–22. 18. Moreno P, Boulot J. Comparative study of short-term results between total artificial disc prosthesis and anterior lumbar interbody fusion. Rev Chir Orthop Reparatrice Appar Mot. 2008;94(3):282–8. 19. Moumene M, Geisler FH.  Comparison of biomechanical function at ideal and varied surgical placement for two lumbar artificial disc implant designs: mobile-core versus fixed-core. Spine (Phila Pa 1976). 2007;32(17):1840–51.

339

20. Di Silvestre M, et al. Dynamic stabilization for degenerative lumbar scoliosis in elderly patients. Spine (Phila Pa 1976). 2010;35(2):227–34. 21. Park CK, Ryu KS, Jee WH.  Degenerative changes of discs and facet joints in lumbar total disc replacement using ProDisc II: minimum two-year follow-up. Spine (Phila Pa 1976). 2008;33(16):1755–61. 22. Khoueir P, Kim KA, Wang MY.  Classification of posterior dynamic stabilization devices. Neurosurg Focus. 2007;22(1):E3. 23. Gala RJ, Russo GS, Whang PG. Interspinous implants to treat spinal stenosis. Curr Rev Musculoskelet Med. 2017;10(2):182–8. 24. Kaibara T, et al. Biomechanics of a lumbar interspinous anchor with transforaminal lumbar interbody fixation. World Neurosurg. 2010;73(5):572–7. 25. Lee CH, et  al. Can the Interspinous device, SPIRE(TM), be an alternative fixation modality in posterior lumbar fusion instead of pedicle screw? Turk Neurosurg. 2017;27(3):408–13. 26. Leivseth G, et  al. Mobility of lumbar segments instrumented with a ProDisc II prosthesis: a two-­ year follow-up study. Spine (Phila Pa 1976). 2006;31(15):1726–33. 27. Kim HJ, et al. Posterior interspinous fusion device for one-level fusion in degenerative lumbar spine disease: comparison with pedicle screw fixation  - preliminary report of at least one year follow up. J Korean Neurosurg Soc. 2012;52(4):359–64. 28. Moojen WA, et  al. Effectiveness of interspinous implant surgery in patients with intermittent neurogenic claudication: a systematic review and meta-­ analysis. Eur Spine J. 2011;20(10):1596–606. 29. Eser O, et al. Dynamic stabilisation in the treatment of degenerative disc disease with modic changes. Adv Orthop. 2013;2013:806267. 30. Highsmith JM, Tumialán LM, Rodts GE Jr. Flexible rods and the case for dynamic stabilization. Neurosurg Focus. 2007;22(1):E11. 31. Niosi CA, et al. The effect of dynamic posterior stabilization on facet joint contact forces: an in  vitro investigation. Spine (Phila Pa 1976). 2008;33(1): 19–26. 32. Musacchio MJ, et  al. Evaluation of decompression and Interlaminar stabilization compared with decompression and fusion for the treatment of lumbar spinal stenosis: 5-year follow-up of a prospective, randomized, controlled trial. Int J Spine Surg. 2016; 10:6. 33. Tyagi V, et al. Posterior dynamic stabilization of the lumbar spine review of biomechanical and clinical studies. Bull Hosp Jt Dis (2013). 2018;76(2):100–4.

Artificial Disc Replacement for Cervical Spine Jung-Woo Hur, Doo Yong Choi, and Seungchan Yoo

1 Introduction For many years, anterior cervical discectomy and fusion (ACDF) has been the gold standard procedure for symptomatic cervical disc disease (CDD) [1–3]. The ACDF procedure is a reliable method for achieving successful clinical outcomes with wide neural decompression and spinal stabilization [4, 5]. Even though successful clinical outcomes can be achieved, ACDF poses a number of limitations, including loss of cervical range of motion (ROM), postoperative dysphagia, pseudoarthrosis or nonunion, instrument failure, and increased segmental motion at adjacent disc segment [1, 6, 7]. Adjacent segment degeneration after cervical fusion remains a major concern and is a direct result of altered biomechanics of the normal cervical spine motion [1, 8]. Elimination of motion at any given level can lead to increased stress across disc spaces above and below the construct, accelerating the degenerative process [9, 10]. The radiologic demonstration of such phenomenon is defined as adjacent segment degenerations, and symptomatic degeneration resulting in spondylotic radiculopathy or myelopathy as a conseJ.-W. Hur Eunpyeong St. Mary’s Hospital, The Catholic University of Korea, Seoul, Republic of Korea D. Y. Choi (*) · S. Yoo Incheon St. Mary’s Hospital, The Catholic University of Korea, Incheon, Republic of Korea

quence is diagnosed as adjacent segment disease (ASD) [11–13]. Researchers have demonstrated the occurrence of postoperative adjacent segment disease in many clinical studies. Hilibrand et al. reported that annually 2.9% of the patients who underwent ACDF will most likely develop ASD requiring additional cervical intervention [14]. In this 10 years follow-up study, authors estimated 25% of patients will develop radiologic evidence of adjacent segment degeneration, of which two-­ thirds would eventually progress to ASD requiring additional surgery. Bydon et al. reported that patients are more likely to develop ASD at cranial segment above the index level of fusion compared to caudal segment, and predicted 31% rate of ASD development at 10 years [15]. Over the years, spine surgeons have been attempting to find an alternative procedure to avoid unwanted postoperative complications associated with ACDF.  Biomechanical analyses demonstrated that ACDF increased intradiscal pressure and ROM during flexion and extension motion [8, 9]. Therefore, theoretically, preserved motion may decrease the stress at adjacent disc levels and consequently can reduce iatrogenic adjacent segment degeneration compared to fusion surgery [3, 16]. Recently, artificial disc replacement (ADR) or cervical disc arthroplasty (CDA) for cervical spine has become popular and widely regarded as an acceptable alternative sur-

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 Y. Ahn et al. (eds.), Core Techniques of Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-981-19-9849-2_31

341

J.-W. Hur et al.

342

gical treatment for symptomatic CDD to reduce ASD [1, 9]. ADR was initially developed to preserve and restore subaxial cervical physiologic biomechanics and natural segmental motion [2, 11]. As a motion-preserving procedure, it was designed to avoid the complications associated with fusion, to alleviate the adjacent level loads, and eventually reduce or eliminate the risk of developing ASD [10, 12]. In the past years, a series of randomized controlled trials (RCT) have been conducted and promisingly, the clinical data proved that preoperative motion could be maintained [2, 10, 13]. Recent studies also suggested that ADR surgery is cost-effective and its clinical results are comparable to ACDF in long-term follow-ups [6, 17].

2 Indications Careful patient selection is the key to achieving favorable outcomes in patients undergoing cervical disc arthroplasty. Current indications for CADR include single or two contiguous level cervical disc disease between C3 and C7 in adult patients with the clinical presentation of cervical radiculopathy and/or myelopathy, which has been unresponsive to conservative treatment [18– 22]. Indications to CADR are summarized in Table 1. Contraindications to CADR include metabolic bone disease or osteoporosis, known as malignancy, inflammatory spondyloarthropathy, facet Table 1 Indications replacement

for

cervical

artificial

disc

Indications  • Single or two contiguous levels between C3 and C7 for conditions:      – Intractable radiculopathy (with or without neck pain) and/or myelopathy  •  And at least one of the following:      – Herniated nucleus pulposus      – Spondylosis (defined by osteophytes)      – Visible loss of disc height compared to adjacent levels  •  Skeletally mature patient  •  Failure of 6 weeks of conservative care  •  No contraindications

arthritis, ossification of posterior longitudinal ligament (OPLL), prior surgery at the index level, active or prior infection, allergy to implant materials, congenital cervical stenosis, and segmental cervical instability [18–22]. The index disc height should be 3 mm or more to ensure the insertion of the device does not result in a large distraction that imposes excessive stress on the posterior cervical structures [23]. Patients with dynamic instability (>3.5 mm translation on flexion-extension lateral radiographs) are not indicated for cervical arthroplasty because mobility preservation would not be desired [18, 20, 21]. Preexisting cervical kyphotic deformity greater than 15° is considered contraindication for cervical arthroplasty because severe kyphotic deformity will typically coexist with posterior spinal pathology (ligamentum flavum hypertrophy, facet capsule thickening, etc. [18, 24] Patients with severe axial neck pain due to facet arthropathy should also be counseled appropriately because these symptoms may not improve, and when severe arthropathy is contributing to instability, CADR may not be the optimal surgical option [18]. Currently, there are no CADR devices that gained US FDA approval for use in greater than 2 contiguous levels, or in conjunction with a previously or concurrently implanted adjacent level ACDF (i.e., Hybrid constructs) [20]. Limitedly, multilevel (3- or 4-level) CADR can be performed in patients with milder or moderate forms of multilevel radiculopathy/myelopathy [24]. Advanced disc degenerative Modic changes (>grade 2), facet degeneration related to axial neck pain, as well as a circumferential cord compression (a section around the cord